Marine vessel propulsion system and marine vessel including the same

ABSTRACT

A marine vessel propulsion system includes first and second propulsion devices, a first operation lever arranged to be operated by a marine vessel maneuvering operator to control the first propulsion device, a second operation lever arranged to be operated by the marine vessel maneuvering operator to control the second propulsion device, a first lever position sensor arranged to detect a position of the first operation lever, a second lever position sensor arranged to detect a position of the second operation lever, and a control unit. The control unit is programmed to set a target pivoting speed according to the positions of the first and second operation levers relative to each other and set a target travel speed according to amounts of displacement of the first and second operation levers with respect to neutral positions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a marine vessel propulsion systemincluding operation levers arranged to be operated for controlling therespective shift states of multiple propulsion devices. The presentinvention also relates to a marine vessel including such a system.

2. Description of the Related Art

There has been known a marine vessel propulsion system includingoperation levers arranged to be operated by a marine vessel maneuveringoperator to control the respective shift states of multiple propulsiondevices. One example of such a propulsion device is an outboard motor.

Such amarine vessel propulsion system includes, for example, twooutboard motors mounted on a hull. The two outboard motors are coupledto each other with a tie bar and arranged to have substantially the samesteering angle. The marine vessel propulsion system further includes twooperation levers corresponding to the two respective outboard motors.The shift state and throttle opening degree of each outboard motor canbe adjusted independently by operating the corresponding operationlever. In addition, the two outboard motors are steerable through onesteering mechanism.

The thus arranged marine vessel propulsion system requires a complicatedoperation when finely controlling the movement of the marine vessel,such as when launching from and docking on shore. That is, the operatoris required to finely control both the steering mechanism and the twooperation levers.

The hull may include a side thruster (propulsion device for lateralmovement) for easier marine vessel maneuvering when launching from anddocking on shore. This, however, results in the marine vessel propulsionsystem having a complex structure, and is not suitable particularly forsmall marine vessels.

United States Patent Application Publication No. US 2007/0017426A1discloses a marine vessel propulsion system that can finely control themovement of a marine vessel easily without providing a side thruster.

This marine vessel propulsion system includes two operation leverscorresponding, respectively, to two outboard motors and a cross-shapedkey provided separately from the two operation levers. The shift stateand throttle opening degree of each outboard motor can be adjustedindependently by operating the corresponding operation lever. Inaddition, the two outboard motors are steerable through one steeringmechanism. This marine vessel propulsion system can set a marine vesselmaneuvering support mode. In the marine vessel maneuvering support mode,operating the cross-shaped key causes the steering angle, shift state,and throttle opening degree of each outboard motor to be adjusted sothat the hull moves in the direction indicated by the cross-shaped key.This allows the movement of the marine vessel to be controlled finelyand easily without a side thruster.

SUMMARY OF THE INVENTION

The inventors of preferred embodiments of the present inventiondescribed and claimed in the present application conducted an extensivestudy and research regarding a marine vessel propulsion system, such asthe one described above, and in doing so, discovered and firstrecognized new unique challenges and previously unrecognizedpossibilities for improvements as described in greater detail below.

That is, the related art above requires two operation levers and across-shaped key to be provided separately, resulting in the marinevessel propulsion system having a complex structure. That is, eventhough no side thruster is provided, an additional operation systemdefined by the cross-shaped key, must be provided in addition to theoperation levers and the steering mechanism. This results in an overlycomplex structure and requires somewhat more complicated operations dueto an increase in the number of operation systems.

In order to overcome the previously unrecognized and unsolved challengesdescribed above, a preferred embodiment according to an aspect of thepresent invention provides a marine vessel propulsion system includingfirst and second propulsion devices arranged to be mounted on a hull soas to enable a steering angle to change, a first operation leverarranged to be operated by a marine vessel maneuvering operator tocontrol the first propulsion device to have a shift state selected fromamong a forward drive state, a neutral state, and a reverse drive stateand to control a power output of the first propulsion device, a secondoperation lever arranged to be operated by the marine vessel maneuveringoperator to control the second propulsion device to have a shift stateselected from among a forward drive state, a neutral state, and areverse drive state and to control a power output of the secondpropulsion device, a first lever position sensor arranged to detect aposition of the first operation lever, a second lever position sensorarranged to detect a position of the second operation lever, and acontrol unit. The control unit is programmed to set, based on detectionresults from the first and second lever position sensors, a targetpivoting speed according to the positions of the first and secondoperation levers relative to each other and to set a target travel speedaccording to amounts of displacement of the first and second operationlevers with respect to neutral positions. The control unit is furtherprogrammed to control the steering angles, shift states, and propulsiveforces of the respective first and second propulsion devices such thatthe hull pivots at the target pivoting speed and travels at the targettravel speed.

In the thus arranged marine vessel propulsion system, the targetpivoting speed and target travel speed of the hull are set based on thepositions of the first and second operation levers. The steering angles,shift states, and propulsive forces of the first and second propulsiondevices are then controlled according to the set target pivoting speedand target travel speed. That is, not only the shift states andpropulsive forces but also the steering angles follow the positions ofthe first and second operation levers. This arrangement allows thepropulsive forces of the propulsion devices to be used effectively whenthe hull pivots or turns (pivots while moving forward or backward). Thisallows the behavior of the hull to be changed quickly and highlyresponsively. As a result, the movement of the marine vessel can befinely controlled.

In addition, since the marine vessel can be controlled by only operatingthe operation levers, there is no need to operate a steering operationmechanism such as a steering mechanism. It is therefore possible toimprove the operability when finely controlling the movement of themarine vessel. There is also no need to provide another operationsystem, such as a cross-shaped key, separately from the operationlevers, which can prevent the marine vessel propulsion system fromhaving a complex structure. Since there is no need to add anotheroperation system, no complicated operations are required.

In a preferred embodiment of the present invention, the control unit isprogrammed to set the target pivoting speed according to a differencebetween the positions of the first and second operation levers detectedby the first and second lever position sensors. This arrangement allowsthe operator to set the target pivoting speed through an intuitiveoperation.

Also, in a preferred embodiment of the present invention, the controlunit is programmed to set the target travel speed according to theposition of one of the first and second operation levers having asmaller amount of displacement with respect to the neutral positionthereof. This arrangement allows the operator to set the target travelspeed through an intuitive operation.

In a preferred embodiment of the present invention, the control unit isprogrammed to set the target travel speed to zero when the firstoperation lever is on one side with respect to the neutral positionthereof and the second operation lever is on the other side with respectto the neutral position thereof. This arrangement allows the operator toeasily perform marine vessel maneuvering by which the hull pivotswithout substantially moving forward or backward.

In a preferred embodiment of the present invention, the first and secondoperation levers are arranged laterally, the first operation lever beingarranged on the right and arranged to be operated back and forth, whilethe second operation lever being arranged on the left and arranged to beoperated back and forth, and the control unit is programmed to set thetarget pivoting speed such that the hull pivots counterclockwise whenthe first operation lever is positioned anterior to the second operationlever, while the hull pivots clockwise when the first operation lever ispositioned posterior to the second operation lever. With thisarrangement, the positions of the first and second operation leverscorrespond to the pivoting direction and the pivoting speed, whichallows the hull to pivot through a more intuitive operation.

In a preferred embodiment of the present invention, the control unit isprogrammed to control each propulsion device to have a constant poweroutput (e.g., minimum power output) when a moment (e.g., greater thanzero) applied by each propulsion device to the hull is equal to orsmaller than a predetermined threshold value, and to control thesteering angle of each propulsion device according to the appliedmoment. This arrangement causes the moment to be adjusted depending onthe change in the steering angle, which requires a smaller amount ofenergy than in the case of increasing the power output of eachpropulsion device.

In the case above, the control unit is preferably programmed to controleach propulsion device to have a maximum steering angle when the momentapplied by each propulsion device to the hull is larger than thepredetermined threshold value, and to control each propulsion device tohave a power output according to the moment. This arrangement allows alarge moment that cannot be generated by only controlling the steeringangle to be generated by controlling the propulsive force. In addition,since the moment is adjusted by controlling the steering angle until thesteering angle of each propulsion device reaches the maximum steeringangle, the energy consumption by the propulsion device can be reduced.

In a preferred embodiment of the present invention, the control unit isprogrammed to set the steering angle of one of the first and secondpropulsion devices such that the direction of the propulsive force ofthe one propulsion device follows a straight line that passes throughthe rotational center of the hull and to set the steering angle, shiftstate, and propulsive force of the other of the first and secondpropulsion devices according to the target pivoting speed. With thisarrangement, the propulsive force of the one propulsion device applies avery small moment to the hull and therefore hardly contributes to thepivoting of the hull. It is therefore only required to set the steeringangle, shift state, and propulsive force of the other propulsion deviceaccording to the target pivoting speed, which facilitates the controloperation for achieving the target pivoting speed.

In the case above, the control unit is preferably programmed to set theshift state and propulsive force of the one propulsion device accordingto an anteroposterior component of the propulsive force of the otherpropulsion device and the target travel speed. It should be noted thatthe anteroposterior component is a component of the propulsive forcegenerated by the selected outboard motor in the longitudinal directionof the hull. With this arrangement, the effect of the anteroposteriorcomponent of the propulsive force of the other propulsion device thatapplies a moment to the hull can be eliminated by the propulsive forceof the one propulsion device. This allows for achieving both the targetpivoting speed and target travel speed. When the target travel speed iszero, for example, the entire anteroposterior component of thepropulsive force of the other propulsion device is canceled by thepropulsive force of the one propulsion device.

A preferred embodiment of the present invention further includes, asteering operation mechanism arranged to be operated by the marinevessel maneuvering operator to change the steering angles of the firstand second propulsion devices, an operation angle sensor arranged todetect an operation angle of the steering operation mechanism, and aswitching unit arranged to switch between normal marine vesselmaneuvering control and assisted marine vessel maneuvering control. Inthis case, in the normal marine vessel maneuvering control, the controlunit is preferably programmed to control the shift states and propulsiveforces of the first and second propulsion devices based on detectionresults from the first and second lever position sensors, and to changethe steering angles of the first and second propulsion devices based ona detection result from the operation angle sensor. Further, in theassisted marine vessel maneuvering control, the control unit ispreferably programmed to set, based on detection results from the firstand second lever position sensors, a target pivoting speed according tothe positions of the first and second operation levers relative to eachother and set a target travel speed according to the amounts ofdisplacement of the first and second operation levers with respect tothe neutral positions, and to control the steering angles, shift states,and propulsive forces of the respective first and second propulsiondevices such that the hull pivots at the target pivoting speed andtravels at the target travel speed. This arrangement allows forswitching between the normal marine vessel maneuvering control and theassisted marine vessel maneuvering control. In the normal marine vesselmaneuvering control, the operator can use the steering operationmechanism for steering. When it is required to finely control themovement of the marine vessel (such as when launching from and dockingon shore), the operator can use only the operation levers for steeringby switching to the assisted marine vessel maneuvering control.

In the assisted marine vessel maneuvering control, the control unit maybe programmed to control each of the first and second propulsion devicesto have a propulsive force smaller than that corresponding to theposition of each of the first and second operation levers in the normalmarine vessel maneuvering control.

In a preferred embodiment of the present invention, the first propulsiondevice includes a first outboard motor arranged to be mounted on thehull so as to enable the steering angle to change, and the secondpropulsion device includes a second outboard motor arranged to bemounted on the hull so as to enable the steering angle to change. Eachof the first and second outboard motors includes, for example, an enginewith a driving force thereof being adjustable through control ofthrottle opening degree, a propeller arranged to be rotated by a drivingforce from the engine, and a switching mechanism portion arranged toswitch shift states. In this case, the first and second operation leversare preferably arranged to be operated by the marine vessel maneuveringoperator to control the first and second outboard motors to be theirrespective shift states and throttle opening degrees. The control unitis preferably programmed to control the steering angles, shift states,and throttle opening degrees of the respective first and second outboardmotors based on detection results from the first and second leverposition sensors. With this arrangement, the marine vessel propulsionsystem including outboard motors can improve the operability when finelycontrolling the movement of the marine vessel.

A preferred embodiment according to another aspect of the presentinvention includes multiple propulsion devices arranged to be mounted ona hull so as to enable a steering angle to change, multiple operationlevers, multiple lever position sensors, a storage unit, and a controlunit. The multiple operation levers are arranged to be operated by amarine vessel maneuvering operator to control the multiple propulsiondevices to have respective shift states selected from among a forwarddrive state, a neutral state, and a reverse drive state. The leverposition sensors are provided correspondingly to the respective multipleoperation levers and arranged to detect positions of the operationlevers. The storage unit is arranged to store therein behavior patternsof the hull preset correspondingly to positional relationships betweenthe multiple operation levers. The control unit is programmed to selectamong the behavior patterns based on detection results from the multiplelever position sensors, and to control the steering angles and shiftstates of the respective multiple propulsion devices to correspond tothe selected behavior pattern. The behavior patterns of the hull may bestored in a form of configuration information for realizing the behaviorpatterns. Such configuration information includes, for example, targetvalues of the steering angles and shift states of multiple propulsiondevices.

In the thus arranged marine vessel propulsion system, selection is madeamong the behavior patterns of the hull based on detection results fromthe multiple lever position sensors. The steering angles and shiftstates of the respective multiple propulsion devices are then controlledto correspond to the selected behavior pattern. That is, not only theshift states but also the steering angles follow the detection resultsfrom the lever position sensors. The behavior patterns of the hullinclude, for example, pivoting and lateral movement. If the operatorwants the hull to behave a certain way, the operator operates multipleoperation levers so as to have a positional relationship correspondingto the desired behavior. This allows the steering angles and shiftstates of the propulsion devices to be controlled automatically to beappropriate to achieve the desired hull behavior. This arrangementallows the propulsive forces of the propulsion devices to be usedeffectively when the hull pivots or moves laterally, for example. Thisallows the behavior of the hull to be changed quickly and highlyresponsively. As a result, the movement of the marine vessel can befinely controlled.

In addition, since the marine vessel can be controlled only by operatingthe operation levers, there is no need to operate a steering operationsystem such as a steering mechanism. It is therefore possible to improvethe operability when finely controlling the movement of the marinevessel. There is also no need to provide another operation system suchas a cross-shaped key separately from the operation levers, which canprevent the marine vessel propulsion system from having a complexstructure. Since there is no need to add another operation system, nocomplicated operations are required.

In a preferred embodiment of the present invention, the multiplepropulsion devices include a first propulsion device and a secondpropulsion device which is different from the first propulsion device.The multiple operation levers also include a first operation levercorresponding to the first propulsion device and a second operationlever corresponding to the second propulsion device. The control unit isprogrammed to select among behavior patterns preset correspondingly tothe positional relationships between the first and second operationlevers when a position of the first operation lever is different from aposition of the second operation lever, and to control the steeringangles and shift states of the respective first and second propulsiondevices to correspond to the selected behavior pattern. For example,when the position of the first operation lever is different from theposition of the second operation lever, the hull may exhibit a behaviorother than straight travel, such as pivoting or lateral movement. Inthis case, the hull moves straight ahead when the first and secondoperation levers are in the same position, while exhibiting a behaviorother than straight movement when the first and second operation leversare in their respective different positions. Since this behavior issimilar to a behavior of the hull through a normal operation of theoperation levers, it is possible to prevent the operator from having anunnatural feeling.

In a preferred embodiment of the present invention, the first and secondoperation levers are arranged laterally. The control unit is thenprogrammed to control the steering angles, shift states of therespective first and second propulsion devices, when the position of thefirst operation lever is different from the position of the secondoperation lever, such that the hull moves in a direction correspondingto a direction from the position of the first operation lever to theposition of the second operation lever. The operator may operate thefirst and second operation levers to orient the direction of a linesegment between the levers to a direction in which he/she wants to movethe hull. This allows the hull to be moved in that direction and therebythe marine vessel to be controlled easily.

In the case above, the control unit is preferably programmed to controlthe steering angles, shift states, and propulsive forces of therespective first and second propulsion devices, when the first operationlever is in the neutral position and the second operation lever is in aposition other than the neutral position, such that the hull moves in adirection corresponding to a direction from the position of the firstoperation lever in the neutral position to the position of the secondoperation lever in the position other than the neutral position. Forexample, when the first operation lever is in the neutral position, thehull can move in the direction from the position of the first operationlever to the position of the second operation lever on the basis of theposition of the first operation lever. Thus, using the neutral positionas a basis for the movement direction of the hull allows the operator toset the movement direction of the hull easily.

The marine vessel propulsion system according to a preferred embodimentof the present invention further includes a steering operation mechanismarranged to be operated by the marine vessel maneuvering operator tochange the steering angles of the respective multiple propulsiondevices, an operation angle sensor arranged to detect an operation angleof the steering operation mechanism, and a switching unit arranged toswitch between normal marine vessel maneuvering control and assistedmarine vessel maneuvering control. In this case, in the normal marinevessel maneuvering control, the control unit may preferably beprogrammed to control the shift states and propulsive forces of thepropulsion devices based on detection results from the multiple leverposition sensors, and to change the steering angles of the multiplepropulsion devices based on a detection result from the operation anglesensor. Further, in the assisted marine vessel maneuvering control, thecontrol unit may preferably be programmed to select among behaviorpatterns corresponding to the positional relationships between themultiple operation levers based on detection results from the multiplelever position sensors, and to control the steering angles and shiftstates of the respective multiple propulsion devices to correspond tothe selected behavior pattern. This arrangement allows for switchingbetween the normal marine vessel maneuvering control and the assistedmarine vessel maneuvering control. In the normal marine vesselmaneuvering control, the operator can use the steering operationmechanism for steering. When it is required to finely control themovement of the marine vessel (such as when launching from and dockingon shore), the operator can use only the operation levers for steeringby switching to the assisted marine vessel maneuvering control.

In the case above, in the assisted marine vessel maneuvering control,the control unit may preferably be programmed to control each of thepropulsion devices to have a propulsive force smaller than thatcorresponding to the position of each operation lever in the normalmarine vessel maneuvering control.

Also, in the assisted marine vessel maneuvering control, the controlunit may preferably be programmed to select among behavior patternspreset correspondingly to the positional relationships between themultiple operation levers, based on detection results from the multiplelever position sensors and irrespective of the relationship between thepositions of the operation levers and the shift states of the propulsiondevices in the normal marine vessel maneuvering control, and to controlthe steering angles and shift states of the respective multiplepropulsion devices to correspond to the selected behavior pattern. Inthe assisted marine vessel maneuvering control, the operator may operatethe operation levers such that the levers are in a positionalrelationship corresponding to a behavior into which he/she wants tobring the hull without regard to the shift states of the propulsiondevices. This allows the hull to perform the desired behavior easily.

Each of the propulsion devices preferably includes an outboard motorarranged to be mounted on the hull so as to enable the steering angle tochange. The outboard motor includes, for example, an engine with adriving force thereof being adjustable through control of throttleopening degree, a propeller arranged to be rotated by a driving forcefrom the engine, and a switching mechanism portion arranged to switchshift states. Also, the operation levers are preferably arranged to beoperated by the marine vessel maneuvering operator to control themultiple outboard motors to be in their respective shift states andthrottle opening degrees. Also, the control unit is preferablyprogrammed to select among the behavior patterns based on detectionresults from the multiple lever position sensors, and to control thesteering angles and shift states of the respective multiple outboardmotors to correspond to the selected behavior pattern. With thisarrangement, the marine vessel propulsion system including outboardmotors can improve the operability when finely controlling the movementof the marine vessel.

Another preferred embodiment of the present invention provides a marinevessel including a hull and a marine vessel propulsion system mounted onthe hull and having the above-described features. This arrangement canimprove the operability when finely controlling the movement of themarine vessel while preventing the marine vessel propulsion system fromhaving a complex structure.

Other elements, features, steps, characteristics and advantages of thepresent invention will become more apparent from the following detaileddescription of the preferred embodiments with reference to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the overall configuration of amarine vessel propulsion system according to a first preferredembodiment of the present invention.

FIG. 2 is a schematic plan view showing the overall configuration of themarine vessel propulsion system.

FIG. 3 is a schematic plan view of a control lever in the marine vesselpropulsion system.

FIG. 4 is a side view of an outboard motor in the marine vesselpropulsion system.

FIG. 5 is a block diagram showing the electrical configuration of themarine vessel propulsion system.

FIGS. 6A and 6B illustrate settings of target values in an assistedmarine vessel maneuvering mode.

FIG. 7 is a graph showing an example of target pivoting speed settingbased on the difference between lever positions.

FIG. 8 is a graph showing an example of target travel speed settingbased on the minimum displacement position.

FIG. 9 is a graphical plan view showing a basic posture of outboardmotors immediately after being switched to the assisted marine vesselmaneuvering mode.

FIG. 10 illustrates the operation when right and left operation leversare operated to be in the same position on the forward drive side in theassisted marine vessel maneuvering mode.

FIG. 11 illustrates the operation when the right and left operationlevers are operated to be in the same position on the reverse drive sidein the assisted marine vessel maneuvering mode.

FIG. 12 shows the state where the right operation lever is on theforward drive side and the left operation lever is in the neutralposition in the assisted marine vessel maneuvering mode, FIG. 12A showsan example of the posture of the outboard motors corresponding to thelever position, and FIG. 12B shows another example of the posture of theoutboard motors corresponding to the lever position.

FIG. 13 shows the state where the right operation lever is on thereverse drive side and the left operation lever is in the neutralposition in the assisted marine vessel maneuvering mode. FIG. 13A showsan example of the posture of the outboard motors corresponding to thelever position. FIG. 13B shows another example of the posture of theoutboard motors corresponding to the lever position.

FIGS. 14A and 14B show another operation example when the rightoperation lever is on the reverse drive side and the left operationlever is in the neutral position in the assisted marine vesselmaneuvering mode.

FIG. 15 illustrates a moment applied by the left outboard motor to thehull.

FIG. 16 is a flow chart illustrating the processing in a hull ECU.

FIG. 17 is a flow chart illustrating pivoting moment generation controland translation suppression control (Steps S6 and S7 in FIG. 16) indetail.

FIG. 18 is a graph illustrating an example of the relationship betweenthe target pivoting moment and the steering angle of each outboardmotor.

FIG. 19 is a schematic plan view of a marine vessel in which threeoutboard motors are mounted on a hull.

FIG. 20 is a schematic plan view of a marine vessel in which fouroutboard motors are mounted on a hull.

FIG. 21 illustrates steering angle control when a marine vesselpropulsion system according to a second preferred embodiment of thepresent invention is in an assisted marine vessel maneuvering mode.

FIG. 22 shows the relationship between the position of each operationlever and the shift state as well as steering angle of each outboardmotor when the marine vessel propulsion system according to the secondpreferred embodiment is in the assisted marine vessel maneuvering mode.

FIG. 23 is a flow chart illustrating the control of the marine vesselpropulsion system according to the second preferred embodiment of thepresent invention.

FIG. 24 illustrates advantageous effects of the marine vessel propulsionsystem according to the second preferred embodiment of the presentinvention.

FIG. 25 shows throttle opening degree control when a marine vesselpropulsion system according to an exemplary variation is in normal andassisted marine vessel maneuvering modes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First PreferredEmbodiment

First, the structure of a marine vessel propulsion system according to afirst preferred embodiment of the present invention will hereinafter bedescribed with reference to FIGS. 1 to 5.

Two outboard motors 300 (right outboard motor 301 and left outboardmotor 302) are mounted at the stern 101 of a hull 100 via two steeringunits 200 (right steering unit 201 and left steering unit 202) (seeFIGS. 2 and 5). A remote control lever 102, a steering operationmechanism 103 such as a steering wheel, a hull ECU (Electronic ControlUnit) 104, a trim switch (not shown), and the like are arranged on thehull 100. The remote control lever 102 is arranged to be operated by amarine vessel maneuvering operator to control switching the throttleopening degrees and shift states of the outboard motors 300. Thesteering operation mechanism 103 is arranged to be operated by theoperator to change the heading direction of the hull 100. The hull ECU104 is programmed to control the marine vessel propulsion system. Thetrim switch is arranged to be operated by the operator to change themounting angle of the outboard motors 300 with respect to the hull 100.The outboard motors 300 and the hull ECU 104 are, respectively, examplesof “propulsion devices” and “control unit” according to a preferredembodiment of the present invention.

The remote control lever 102 includes two operation levers (rightoperation lever 102 a and left operation lever 102 b) that correspond tothe respective right and left outboard motors 301 and 302. The right andleft operation levers 102 a and 102 b are arranged laterally (on theright and left in the direction A) and are arranged to be movablelongitudinally (back and forth in the direction B) independently of eachother. The operator can switch the shift state and perform accelerationcontrol (throttle opening degree control) of the right outboard motor301 by operating the right operation lever 102 a. The operator can alsoswitch the shift state and perform acceleration control of the leftoutboard motor 302 by operating the left operation lever 102 b. Theshift state of the outboard motors 301 and 302 can be selected fromamong neutral state, forward drive state, and reverse drive state. Theright and left operation levers 102 a and 102 b are, respectively,examples of “first operation lever” and “second operation lever”according to a preferred embodiment of the present invention. Also, theright and left outboard motors 301 and 302 are, respectively, examplesof “first propulsion device” and “second propulsion device” according toa preferred embodiment of the present invention.

As shown in FIG. 3, the operation levers (right operation lever 102 aand left operation lever 102 b) are movable among a neutral position, aforward drive position, and a reverse drive position. The neutralposition, forward drive position, and reverse drive position correspond,respectively, to the neutral state, forward drive state, and reversedrive state of the outboard motors 300. The marine vessel propulsionsystem is arranged to change the throttle opening degree (power output)of each outboard motor 300 according to the amount of displacement ofthe corresponding operation lever with respect to the neutral positionwhen the operation lever is in the forward or reverse drive position.That is, the greater the amount of displacement of the operation leverwith respect to the neutral position, the greater the throttle openingdegree of the corresponding outboard motor 300 becomes. The remotecontrol lever 102 includes lever position sensors 102 c and 102 darranged to detect the turning angle of the operation levers, beingprovided correspondingly to the respective right and left operationlevers 102 a and 102 b. The shift states and throttle opening degrees ofthe respective outboard motors 300 (right outboard motor 301 and leftoutboard motor 302) are controlled based on detection results from thelever position sensors 102 c and 102 d.

The steering operation mechanism 103 is also arranged to be operated bythe operator to steer the outboard motors 300 (right outboard motor 301and left outboard motor 302). The steering operation mechanism 103 isprovided with an operation angle sensor 103 a arranged to detect therotation angle of the steering operation mechanism 103.

The steering units 200 (right steering unit 201 and left steering unit202) are each mounted at the stern 101 of the hull 100 via a clampbracket 400. As shown in FIG. 5, the right steering unit 201 includes amotor 201 a arranged to turn the corresponding outboard motor 300 duringsteering, an actual steering angle sensor 201 b arranged to detect theturning angle (actual steering angle) of the outboard motor 300, and asteering ECU 201 c. Similarly, the left steering unit 202 includes amotor 202 a arranged to turn the corresponding outboard motor 300 duringsteering, an actual steering angle sensor 202 b arranged to detect theturning angle (actual steering angle) of the outboard motor 300, and asteering ECU 202 c. The hull ECU 104 and the steering ECUs 201 c and 202c are arranged to be capable of communicating information with eachother via a LAN (Local Area Network) 10 built in the hull 100.

When the motors 201 a and 202 a are driven based on a detection resultfrom the operation angle sensor 103 a, the steering angles of theoutboard motors 300 (right outboard motor 301 and left outboard motor302) are adjusted accordingly. That is, when the bodies of the outboardmotors 300 are turned horizontally, propellers 307 change theirdirection. This changes the heading direction of the hull 100 thatdepends on propulsive forces generated by the propellers 307.

The steering units 200 can change the steering angle of each outboardmotor 300 preferably within an angular range of about 60 degrees (about±30 degrees), for example. When the steering angles of the outboardmotors 300 are adjusted based on a detection result from the operationangle sensor 103 a, the motors 201 a and 202 a are controlled such thatthe right and left outboard motors 301 and 302 have substantially thesame steering angle.

As shown in FIG. 4, the outboard motors 300 each include an engine 303,a drive shaft 304, a forward-reverse switching mechanism 305, apropeller shaft 306, a propeller 307, and an outboard motor ECU 308. Theengine 303 is arranged to generate a driving force by burning a mixtureof air and fuel. The drive shaft 304 extends in the vertical direction(in the Z direction) and is arranged to be rotated by a driving forcefrom the engine 303. The forward-reverse switching mechanism 305 isconnected to the lower end of the drive shaft 304. The propeller shaft306 is connected to the forward-reverse switching mechanism 305 andextends in the horizontal direction. The propeller 307 is fixed at therear end portion of the propeller shaft 306. The outboard motor ECU 308is arranged to control the operations of the engine 303 and theforward-reverse switching mechanism 305. The hull ECU 104 and theoutboard motor ECUs 308 in the right and left outboard motors arearranged to be capable of communicating information with each other viathe LAN 10.

The engine 303 includes a motor 303 a and a throttle valve 303 b. Thethrottle valve 303 b is provided in a feed path for feeding airtherethrough into a mixture combustion chamber (not shown). The throttlevalve 303 b is arranged to be opened and closed by a driving force fromthe motor 303 a within the range from the fully-closed state (with anopening degree of 0%) to the fully-opened state (with an opening degreeof 100%). The motor 303 a is controlled by the outboard motor ECU 308.The driving force of the engine 303 can be adjusted by controlling theopening degree (throttle opening degree) of the throttle valve 303 b andtherefore the feed amount of air.

The forward-reverse switching mechanism 305 is arranged to set a shiftstate selected from among forward drive state, reverse drive state, andneutral state. The forward drive state is a shift state in which therotation of the drive shaft 304 caused by a driving force from theengine 303 is transmitted to rotate the propeller shaft 306 in theforward drive direction. The reverse drive state is a shift state inwhich the rotation of the drive shaft 304 is reversed and transmitted torotate the propeller shaft 306 in the reverse drive direction. Theneutral state is a shift state in which the transmitting of the rotationfrom the drive shaft 304 to the propeller shaft 306 is blocked off. Theshift state is switched by a driving force from a motor 305 a. The motor305 a is controlled by the outboard motor ECU 308.

The outboard motor ECU 308 controls the motors 303 a and 305 a and otherelectrical components in the outboard motor 300 based on signals fromthe hull ECU 104. The forward-reverse switching mechanism 305 is anexample of a “switching mechanism portion” according to a preferredembodiment of the present invention.

The engine 303 is housed in an engine cover 309. An upper case 310 and alower case 311 are arranged below the engine cover 309, and the driveshaft 304 and the forward-reverse switching mechanism 305 as well as thepropeller shaft 306 are housed in the respective cases 310 and 311. Aventilation hole 309 a is provided in a lateral portion of the enginecover 309 on the side of the reverse drive direction (indicated by thearrow B1). Air which is introduced in the engine cover 309 via theventilation hole 309 a, is fed to the engine 303.

The outboard motors 300 are each mounted at the stern 101 of the hull100 via a clamp bracket 400. The clamp bracket 400 supports eachoutboard motor 300 in a vertically swingable manner about a tiltingshaft 400 a with respect to the hull 100.

The hull 100 is provided with a selector switch 105 to be operated bythe operator to switch control modes. The control modes include a normalmarine vessel maneuvering mode in which the steering operation mechanism103 is used for marine vessel maneuvering and an assisted marine vesselmaneuvering mode in which the steering operation mechanism 103 is notrequired to be used for marine vessel maneuvering. One of these controlmodes can be selected by operating the selector switch 105.

In the normal marine vessel maneuvering mode, the shift states andthrottle opening degrees of the respective right and left outboardmotors 301 and 302 are controlled based on detection results from thelever position sensors 102 c and 102 d. The steering angle of theoutboard motors 300 (right outboard motor 301 and left outboard motor302) is also controlled based on a detection result from the operationangle sensor 103 a.

In the assisted marine vessel maneuvering mode, the shift states,throttle opening degrees, and steering angles of the respective rightand left outboard motors 301 and 302 are controlled based on detectionresults from the lever position sensors 102 c and 102 d.

The operator can switch between the normal marine vessel maneuveringmode and the assisted marine vessel maneuvering mode by switching theselector switch 105 ON and OFF. That is, when the selector switch 105 isOFF, the normal marine vessel maneuvering mode runs. When the selectorswitch 105 is ON, the assisted marine vessel maneuvering mode runs. Inthe assisted marine vessel maneuvering mode, when the steering operationmechanism 103 is operated, the selector switch 105 is turned OFFautomatically by the control of the hull ECU 104 and the normal marinevessel maneuvering mode runs automatically. The selector switch 105 isan example of a “switching unit” according to a preferred embodiment ofthe present invention.

In the normal marine vessel maneuvering mode, the hull ECU 104determines the shift states and throttle opening degrees of the rightand left outboard motors 301 and 302 based on positional information ofthe operation levers detected by the lever position sensors 102 c and102 d. These determined shift states and throttle opening degrees aresent to the outboard motor ECUs 308. The outboard motor ECUs 308 controlthe motors 303 a and 305 a based on the received shift states andthrottle opening degrees to drive the throttle valve 303 b and theforward-reverse switching mechanism 305. The hull ECU 104 alsodetermines the steering angles of the right and left outboard motors 301and 302 based on an operation angle detected by the operation anglesensor 103 a, and sends the determined steering angle data to thesteering ECUs 201 c and 202 c. The steering ECUs 201 c and 202 c drivethe motors 201 a and 202 a in the respective right and left steeringunits 201 and 202 to make actual steering angles detected by therespective actual steering angle sensors 201 b and 202 b equal to thereceived steering angles.

FIGS. 6A and 6B are graphical plan views of the remote control lever102, illustrating settings of target values in the assisted marinevessel maneuvering mode. The hull ECU 104 is arranged to set a targetpivoting speed and a target travel speed of the hull 100 based on theposition L1 of the right operation lever 102 a and the position L2 ofthe left operation lever 102 b. The positions L1 and L2 are expressed asa positive value when on the forward drive side with respect to theneutral position, and are expressed as a negative value when on thereverse drive side with respect to the neutral position. The absolutevalues |L1| and |L2| of the positions L1 and L2 are the amounts ofdisplacement of the respective right and left operation levers 102 a and102 b with respect to the neutral position. These positions L1 and L2are obtained as outputs from the lever position sensors 102 c and 102 d.The target pivoting speed of the hull 100 is expressed as a positivevalue in the counterclockwise direction, and is expressed as a negativevalue in the clockwise direction in the plan view. Also, the targettravel speed of the hull 100 is expressed as a positive value in theforward travel direction, and is expressed as a negative value in thereverse travel direction.

The hull ECU 104 subtracts the position L2 of the left operation lever102 b from the position L1 of the right operation lever 102 a to obtaina lever position difference ΔL (=L1−L2). The hull ECU 104 then obtainsthe target pivoting speed based on this lever position difference ΔL.

The hull ECU 104 further determines if the positions L1 and L2 of theright and left operation levers 102 a and 102 b have the same sign ortheir respective different signs. That is, it is determined if the rightand left operation levers 102 a and 102 b are on the same side (forwardor reverse drive side) with respect to the neutral position. If thepositions L1 and L2 of the right and left operation levers 102 a and 102b have their respective different signs, the hull ECU 104 sets thetarget travel speed to zero. On the other hand, if the positions L1 andL2 of the right and left operation levers 102 a and 102 b have the samesign, the hull ECU 104 identifies a smaller one of the amounts ofdisplacement |L1| and |L2| of the right and left operation levers 102 aand 102 b. The hull ECU 104 then obtains the target travel speed basedon the position Lmin (=L1 or L2, hereinafter referred to as “minimumdisplacement position Lmin”) corresponding to the smaller amount ofdisplacement. If either of the absolute amount of displacement |L1| or|L2| is zero, the target travel speed is also set to zero.

FIG. 6A shows the case of ΔL>0 and Lmin=L2>0. Accordingly, the targetpivoting speed is positive and the target travel speed is also positive.As a result, the outboard motors 300 are controlled such that the hull100 pivots counterclockwise while moving forward (i.e., turns in theleft-forward direction). On the other hand, FIG. 6B shows the case ofΔL>0 and Lmin=L2=0. Accordingly, the target pivoting speed is positiveand the target travel speed is zero. As a result, the outboard motors300 are controlled such that the hull 100 pivots counterclockwisesubstantially with no displacement. This behavior of the hull 100 issimilar to a behavior of the hull corresponding to the same leveroperations in the normal marine vessel maneuvering mode. Therefore, theoperator can perform marine vessel maneuvering in the assisted marinevessel maneuvering mode while having an improved and more comfortablenatural feeling.

FIG. 7 is a graph showing an example of target pivoting speed settingbased on the lever position difference ΔL. A dead band with apredetermined width is provided in the vicinity of the lever positiondifference ΔL=0 such that the target pivoting speed is zero if theabsolute value of the lever position difference ΔL is smaller than apredetermined value. When the lever position difference ΔL is greaterthan the dead band, the target pivoting speed is set to a positivevalue. On the other hand, when the lever position difference ΔL issmaller than the dead band, the target pivoting speed is set to anegative value. Then, the absolute target pivoting speed increasesmonotonically (linearly in FIG. 7) with the increase in the absolutevalue of the lever position difference ΔL.

FIG. 8 is a graph showing an example of target travel speed settingbased on the minimum displacement position Lmin. A dead band with apredetermined width is provided in the vicinity of the minimumdisplacement position Lmin=0 such that the target travel speed is zeroif the absolute value of the minimum displacement position Lmin issmaller than a predetermined value. When the minimum displacementposition Lmin is greater than the dead band, the target travel speed isset to a positive value (for forward travel). On the other hand, whenthe minimum displacement position Lmin is smaller than the dead band,the target travel speed is set to a negative value (for reverse travel).Then, the absolute target travel speed increases monotonically (linearlyin FIG. 8) with the increase in the absolute value of the minimumdisplacement position Lmin.

FIG. 9 is a graphical plan view showing a basic posture of the outboardmotors 301 and 302 immediately after being switched to the assistedmarine vessel maneuvering mode. When the selector switch 105 is operatedto run the assisted marine vessel maneuvering mode, the hull ECU 104controls the outboard motors 301 and 302 to be in the basic postureshown in FIG. 9. More specifically, the hull ECU 104 sets the targetsteering angles of the outboard motors 301 and 302 such that thestraight lines 301 a and 302 a in the directions of the propulsiveforces of the respective outboard motors 301 and 302 pass through therotational center 20 of the hull 100 in a plan view. That is, in thebasic posture, the outboard motors 301 and 302 are in a positionalrelationship in which the rear end portions thereof are separated fromeach other. When the target steering angles corresponding to this basicposture are transmitted to the steering ECUs 201 c and 202 c via the LAN10, the right and left outboard motors 301 and 302 are turned to be inthe basic posture shown in FIG. 9. When both the right and leftoperation levers 102 a and 102 b are in the neutral position, ΔL=0 andLmin=0. In this case, the right and left outboard motors 301 and 302 arecontrolled to be in the basic posture, their shift states are controlledto be the neutral position, and their engine speeds are controlled to bean idle speed. That is, the target throttle opening degree is set to afully-closed value correspondingly to the idle speed.

It is noted that the steering angle takes a positive value when the rearend portions (propellers 307) of the outboard motors 301 and 302 areturned rightward with respect to the longitudinal direction of the hull100 (along the hull centerline 21), while taking a negative value whenturned leftward. Thus, in the basic posture, the steering angle of theright outboard motor 301 is positive and the steering angle of the leftoutboard motor 302 is negative.

FIG. 10 shows the state where the right and left operation levers 102 aand 102 b are operated to be in the same position on the forward driveside in the assisted marine vessel maneuvering mode. In this case, sinceΔL=0 and Lmin>0, the target pivoting speed is set to zero and the targettravel speed is set to a positive value. Therefore, the outboard motors301 and 302 are controlled such that the hull 100 moves straight ahead.Specifically, the hull ECU 104 sets the target steering angles of theoutboard motors 301 and 302 to the steering angles in the basic posture.The hull ECU 104 also sets both the target shift states of the outboardmotors 301 and 302 to the forward drive state. The hull ECU 104 furthersets the target throttle opening degrees (target engine speeds) of theoutboard motors 301 and 302 to a value corresponding to the minimumdisplacement position Lmin.

The target steering angles are transmitted to the steering ECUs 201 cand 202 c via the LAN 10. This causes both the outboard motors 301 and302 to be controlled to be in the basic posture and their propulsiveforces (indicated by arrows in FIG. 10) are directed to the rotationalcenter 20 of the hull 100. The target shift states (set to forward drivestate) and the target throttle opening degrees (target engine speeds)are transmitted to the outboard motor ECUs 308 in the right and leftoutboard motors 301 and 302 via the LAN 10. This causes both the shiftstates of the right and left outboard motors 301 and 302 to becontrolled to be the forward drive state, and the right and leftoutboard motors 301 and 302 have approximately the same engine speed. Asa result, the resultant force of the propulsive forces of the right andleft outboard motors 301 and 302 is directed to the forward traveldirection of the hull 100. Since both the propulsive forces of the rightand left outboard motors 301 and 302 act in the direction through therotational center 20 of the hull 100, the hull 100 moves forward withoutsubstantially pivoting. That is, the hull 100 moves forward along itscenterline 21.

FIG. 11 shows the state where the right and left operation levers 102 aand 102 b are operated to be in the same position on the reverse driveside in the assisted marine vessel maneuvering mode. In this case, sinceΔL=0 and Lmin<0, the target pivoting speed is set to zero and the targettravel speed is set to a negative value. Therefore, the outboard motors301 and 302 are controlled such that the hull 100 moves straight astern.Specifically, the hull ECU 104 sets the target steering angles of theoutboard motors 301 and 302 to the steering angles in the basic posture.The hull ECU 104 also sets both the target shift states of the outboardmotors 301 and 302 to the reverse drive state. The hull ECU 104 furthersets the target throttle opening degrees (target engine speeds) of theoutboard motors 301 and 302 to a value corresponding to the minimumdisplacement position Lmin.

The target steering angles are transmitted to the steering ECUs 201 cand 202 c via the LAN 10. This causes both the outboard motors 301 and302 to be controlled to be in the basic posture and their propulsiveforces (indicated by arrows in FIG. 11) are directed backward along therespective straight lines 301 a and 302 a that pass through therotational center 20 of the hull 100. The target shift states (set toreverse drive state) and the target throttle opening degrees (targetengine speeds) are transmitted to the outboard motor ECUs 308 in theright and left outboard motors 301 and 302 via the LAN 10. This causesboth the shift states of the right and left outboard motors 301 and 302to be controlled to the reverse drive state, and the right and leftoutboard motors 301 and 302 have approximately the same engine speed. Asa result, the resultant force of the propulsive forces of the right andleft outboard motors 301 and 302 is directed to the reverse traveldirection of the hull 100. Since both the propulsive forces of the rightand left outboard motors 301 and 302 act in the direction through therotational center 20 of the hull 100, the hull 100 moves backwardwithout substantially pivoting. That is, the hull 100 moves backwardalong its centerline 21.

FIG. 12 shows the state where the right operation lever 102 a is on theforward drive side and the left operation lever 102 b is in the neutralposition in the assisted marine vessel maneuvering mode. In this case,since ΔL>0 and Lmin=0, the target pivoting speed is set to a positivevalue and the target travel speed is set to zero. Therefore, theoutboard motors 301 and 302 are controlled such that the hull 100 pivotscounterclockwise substantially with no displacement. The hull ECU 104controls the outboard motors 301 and 302 to be in the state shown inFIG. 12A or 12B, for example.

FIG. 12A shows the state where the steering angle of the right outboardmotor 301 is made smaller than that in the basic posture and itspropulsive force is directed right-forward with respect to therotational center 20 of the hull 100. The left outboard motor 302 is inthe basic posture. That is, the hull ECU 104 sets the target steeringangle of the right outboard motor 301 to a value smaller than thesteering angle in the basic posture. The hull ECU 104 also sets thetarget shift state of the right outboard motor 301 to the forward drivestate and the target throttle opening degree (target engine speed) ofthe right outboard motor 301 to a value corresponding to the leverposition difference ΔL. This causes the propulsive force of the rightoutboard motor 301 to apply a (counterclockwise) moment about therotational center 20 to the hull 100.

It is, however, noted that the propulsive force of the right outboardmotor 301 also acts as a propulsive force in the forward traveldirection of the hull 100. Hence, the hull ECU 104 controls the leftoutboard motor 302 to generate a propulsive force in the reverse traveldirection. More specifically, the hull ECU 104 sets the target steeringangle of the left outboard motor 302 to a value corresponding to thebasic posture and the target shift state of the left outboard motor 302to the reverse drive state. The hull ECU 104 also sets the targetthrottle opening degree (target engine speed) of the left outboard motor302 to a value with which the propulsive force in the forward traveldirection (anteroposterior component) by the right outboard motor 301can be cancelled. Thus, only a counterclockwise moment about therotational center 20 acts on the hull 100, which allows the hull 100 topivot counterclockwise substantially with no displacement. In moredetail, a moment is applied to the hull 100 by the propulsive force ofthe right outboard motor 301 in the forward travel direction with themovement of the hull 100 being restricted by the left outboard motor302. This results in the hull 100 pivoting in such a manner that itsstern moves leftward.

FIG. 12B shows the state where the steering angle of the left outboardmotor 302 is made greater (smaller in its absolute value) than that inthe basic posture and its propulsive force is directed backward alongthe straight line 302 a that passes on the left of the rotational center20 of the hull 100. The right outboard motor 301 is in the basicposture. That is, the hull ECU 104 sets the target steering angle of theleft outboard motor 302 to a value smaller than the steering angle inthe basic posture. The hull ECU 104 also sets the target shift state ofthe left outboard motor 302 to the reverse drive state and the targetthrottle opening degree (target engine speed) of the left outboard motor302 to a value corresponding to the lever position difference ΔL. Thiscauses the propulsive force of the left outboard motor 302 to apply a(counterclockwise) moment about the rotational center 20 to the hull100.

It is, however, noted that the propulsive force of the left outboardmotor 302 also acts as a propulsive force in the reverse traveldirection of the hull 100. Hence, the hull ECU 104 controls the rightoutboard motor 301 to generate a propulsive force in the forward traveldirection. More specifically, the hull ECU 104 sets the target steeringangle of the right outboard motor 301 to a value corresponding to thebasic posture and the target shift state of the right outboard motor 301to the forward drive state. The hull ECU 104 also sets the targetthrottle opening degree (target engine speed) of the right outboardmotor 301 to a value with which the propulsive force in the reversetravel direction (anteroposterior component) by the left outboard motor302 can be cancelled. Thus, only a (counterclockwise) moment about therotational center 20 acts on the hull 100, which allows the hull 100 topivot counterclockwise with no substantial displacement. In more detail,a moment is applied to the hull 100 by the propulsive force of the leftoutboard motor 302 in the forward drive direction with the movement ofthe hull 100 being restricted by the right outboard motor 301. Thisresults in the hull 100 pivoting in such a manner that its stern movesleftward.

The counterclockwise pivoting can thus be realized in which the stern ofthe hull 100 moves leftward. This facilitates, for example, docking on adocking target 30 such as a quay.

FIG. 13 shows the state where the right operation lever 102 a is on thereverse drive side and the left operation lever 102 b is in the neutralposition in the assisted marine vessel maneuvering mode. In this case,since ΔL<0 and Lmin=0, the target pivoting speed is set to a negativevalue and the target travel speed is set to zero. Therefore, theoutboard motors 301 and 302 are controlled such that the hull 100 pivotsclockwise with no substantial displacement. The hull ECU 104 controlsthe outboard motors 301 and 302 to be the state shown in FIG. 13A or13B, for example.

FIG. 13A shows the state where the steering angle of the left outboardmotor 302 is made smaller (greater in its absolute value) than that inthe basic posture and its propulsive force is directed backward alongthe straight line 302 a that passes on the right of the rotationalcenter 20 of the hull 100. The right outboard motor 301 is in the basicposture. That is, the hull ECU 104 sets the target steering angle of theleft outboard motor 302 to a negative value smaller (greater in itsabsolute value) than the steering angle in the basic posture. The hullECU 104 also sets the target shift state of the left outboard motor 302to the reverse drive state and the target throttle opening degree(target engine speed) of the left outboard motor 302 to a valuecorresponding to the lever position difference ΔL. This causes thepropulsive force of the left outboard motor 302 to apply a (clockwise)moment about the rotational center 20 to the hull 100.

It is, however, noted that the propulsive force of the left outboardmotor 302 also acts as a propulsive force in the reverse traveldirection of the hull 100. Hence, the hull ECU 104 controls the rightoutboard motor 301 to generate a propulsive force in the forward traveldirection. More specifically, the hull ECU 104 sets the target steeringangle of the right outboard motor 301 to a value corresponding to thebasic posture and the target shift state of the right outboard motor 301to the forward drive state. The hull ECU 104 also sets the targetthrottle opening degree (target engine speed) of the right outboardmotor 301 to a value with which the propulsive force in the reversetravel direction (anteroposterior component) by the left outboard motor302 can be cancelled. Thus, only a clockwise moment about the rotationalcenter 20 acts on the hull 100, which allows the hull 100 to pivotclockwise with no substantial displacement. In more detail, a moment isapplied to the hull 100 by the propulsive force of the left outboardmotor 302 in the reverse travel direction with the movement of the hull100 being restricted by the right outboard motor 301. This results inthe hull 100 pivoting such that its stern moves leftward.

FIG. 13B shows the state where the steering angle of the right outboardmotor 301 is made greater than that in the basic posture and itspropulsive force is directed forward along the straight line 301 a thatpasses on the left of the rotational center 20 of the hull 100. The leftoutboard motor 302 is in the basic posture. That is, the hull ECU 104sets the target steering angle of the right outboard motor 301 to avalue greater than the steering angle in the basic posture. The hull ECU104 also sets the target shift state of the right outboard motor 301 tothe forward drive state and the target throttle opening degree (targetengine speed) of the right outboard motor 301 to a value correspondingto the lever position difference ΔL. This causes the propulsive force ofthe right outboard motor 301 to apply a (clockwise) moment about therotational center 20 to the hull 100.

It is, however, noted that the propulsive force of the right outboardmotor 301 also acts as a propulsive force in the forward traveldirection of the hull 100. Hence, the hull ECU 104 controls the leftoutboard motor 302 to generate a propulsive force in the reverse traveldirection. More specifically, the hull ECU 104 sets the target steeringangle of the left outboard motor 302 to a value corresponding to thebasic posture and the target shift state of the left outboard motor 302to the reverse drive state. The hull ECU 104 also sets the targetthrottle opening degree (target engine speed) of the left outboard motor302 to a value with which the propulsive force in the forward traveldirection (anteroposterior component) applied by the right outboardmotor 301 can be cancelled. Thus, only a clockwise moment about therotational center 20 acts on the hull 100, which allows the hull 100 topivot clockwise with no substantial displacement. In more detail, amoment is applied to the hull 100 by the propulsive force of the rightoutboard motor 301 in the forward travel direction with the movement ofthe hull 100 being restricted by the left outboard motor 302. Thisresults in the hull 100 pivoting such that its stern moves leftward.

The clockwise pivoting can thus be realized in which the stern of thehull 100 moves leftward. This facilitates, for example, docking on adocking target 30 such as a quay.

Repeating the operation (leftward movement of the stern) shown in FIGS.12, 12A, and 12B and the operation (leftward movement of the stern)shown in FIGS. 13, 13A, and 13B alternately allows the hull 100 to moveleftward. That is, when the left operation lever 102 b is kept in theneutral position, the stern can move leftward by operating the rightoperation lever 102 a to the forward drive side. The stern can also moveleftward by operating the right operation lever 102 a to the reversedrive side.

FIGS. 14A and 14B show another operation example when the rightoperation lever 102 a is on the reverse drive side and the leftoperation lever 102 b is in the neutral position (see FIG. 13) in theassisted marine vessel maneuvering mode.

FIG. 14A shows the state where the steering angle of the right outboardmotor 301 is made smaller than that in the basic posture to be anegative value and its propulsive force is directed backward along thestraight line 301 a that passes on the right of the rotational center 20of the hull 100. The left outboard motor 302 is in the basic posture. Inthis operation example, the propulsive force of the right outboard motor301 follows the straight line 301 a, which is rotated further clockwiserelative to the straight line 302 a that the propulsive force of theleft outboard motor 302 follows. This causes the propulsive force of theright outboard motor 301 to apply a larger moment to the hull 100. Thehull ECU 104 sets the target steering angle of the right outboard motor301 to a negative value. The hull ECU 104 also sets the target shiftstate of the right outboard motor 301 to the reverse drive state and thetarget throttle opening degree (target engine speed) of the rightoutboard motor 301 to a value corresponding to the lever positiondifference ΔL. This causes the propulsive force of the right outboardmotor 301 to apply a (clockwise) moment about the rotational center 20to the hull 100.

It is, however, noted that the propulsive force of the right outboardmotor 301 also acts as a propulsive force (anteroposterior component) inthe reverse travel direction of the hull 100. Hence, the hull ECU 104controls the left outboard motor 302 to generate a propulsive force inthe forward travel direction. More specifically, the hull ECU 104 setsthe target steering angle of the left outboard motor 302 to a valuecorresponding to the basic posture and the target shift state of theleft outboard motor 302 to the forward drive state. The hull ECU 104also sets the target throttle opening degree (target engine speed) ofthe left outboard motor 302 to a value with which the propulsive forcein the reverse travel direction by the right outboard motor 301 can becancelled. Thus, only a clockwise moment about the rotational center 20acts on the hull 100, which allows the hull 100 to pivot with nosubstantial displacement so that its stern moves leftward.

FIG. 14B shows the state where the steering angle of the left outboardmotor 302 is made greater than that in the basic posture to be apositive value and its propulsive force is directed forward along thestraight line 302 a that passes on the left of the rotational center 20of the hull 100. The right outboard motor 302 is in the basic posture.In this operation example, the direction of the propulsive force of theleft outboard motor 302 follows the straight line, which is rotatedfurther counterclockwise relative to the straight line 301 a that thepropulsive force of the right outboard motor 301 follows. This causesthe propulsive force of the left outboard motor 302 to apply a largermoment to the hull 100.

The hull ECU 104 sets the target steering angle of the left outboardmotor 302 to a (positive) value greater than the steering angle in thebasic posture. The hull ECU 104 also sets the target shift state of theleft outboard motor 302 to the forward drive state and the targetthrottle opening degree (target engine speed) of the left outboard motor302 to a value corresponding to the lever position difference ΔL. Thiscauses the propulsive force of the left outboard motor 302 to apply a(clockwise) moment about the rotational center 20 to the hull 100.

It is, however, noted that the propulsive force of the left outboardmotor 302 also acts as a propulsive force (anteroposterior component) inthe forward travel direction of the hull 100. Hence, the hull ECU 104controls the right outboard motor 301 to generate a propulsive force inthe reverse travel direction. More specifically, the hull ECU 104 setsthe target steering angle of the right outboard motor 301 to a valuecorresponding to the basic posture and the target shift state of theright outboard motor 301 to the reverse drive state. The hull ECU 104also sets the target throttle opening degree (target engine speed) ofthe right outboard motor 301 to a value with which the propulsive forcein the forward travel direction by the left outboard motor 302 can becancelled. Thus, only a clockwise moment about the rotational center 20acts on the hull 100, which allows the hull 100 to pivot with nosubstantial displacement so that the stern of the hull 100 movesleftward.

Although FIGS. 12 to 14B illustrate the operations for counterclockwisepivoting of the hull 100, the same applies to operations for clockwisepivoting of the hull 100. In this case, the operations of the right andleft operation levers 102 a and 102 b replace each other. Accordingly,the operations of the right and left outboard motors 301 and 302 alsoreplace each other.

FIG. 15 illustrates a moment applied by the left outboard motor 302 tothe hull 100. The distance from the rotational center 20 of the hull 100to the steering axis 25 of the left outboard motor 302 along thelongitudinal direction of the hull 100 (along the hull centerline 21) isdefined as L1. Further, the distance from the rotational center 20 ofthe hull 100 to the steering axis 25 of the left outboard motor 302along the lateral direction of the hull 100 (perpendicular to the hullcenterline 21 in a plan view) is defined as L2. Further, the propulsiveforce of the left outboard motor 302 is defined as T_(L). The steeringangle of the left outboard motor 302 is then defined as θ_(L). In thiscase, the moment M_(L) about the rotational center 20 of the hull 100 isexpressed as follows:M _(L) =T _(L)·(L1·sin θ_(L) +L2·cos θ_(L)).

The moment M_(R) applied by the propulsive force of the right outboardmotor 301 to the hull 100 can also be obtained in the same manner.Summing these moments provides the moment M (=M_(R)+M_(L)) applied tothe hull 100. Accordingly, in the assisted marine vessel maneuveringmode, the direction of the propulsive force of the right or leftoutboard motor 301 or 302 may not necessarily follow a straight linethat passes through the rotational center 20. However, the operation inthis case is complicated. Therefore, in order to simplify the operation,it is preferred that in the assisted marine vessel maneuvering mode, thedirection of the propulsive force of one outboard motor follows astraight line that passes through the rotational center 20 of the hull100 so that the moment M_(L) or M_(R) generated by the one outboardmotor is zero.

FIG. 16 is a flow chart illustrating the processing in the hull ECU 104.In Step S1, the hull ECU 104 determines whether or not the selectorswitch 105 is ON. If the selector switch 105 is OFF, the routine goes toStep S9 and the control under the normal marine vessel maneuvering modeis performed. On the other hand, if the selector switch 105 is ON, thecontrol under the assisted marine vessel maneuvering mode is performedin Step S2.

In the normal marine vessel maneuvering mode, the hull ECU 104determines the shift states and throttle opening degrees of the rightand left outboard motors 301 and 302 based on positional information ofthe operation levers detected by the lever position sensors 102 c and102 d. These determined shift states and throttle opening degrees aresent to the outboard motor ECUs 308. The outboard motor ECUs 308 controlthe motors 303 a and 305 a based on the received shift states andthrottle opening degrees to drive the throttle valve 303 b and theforward-reverse switching mechanism 305. The hull ECU 104 alsodetermines the steering angles of the right and left outboard motors 301and 302 based on an operation angle detected by the operation anglesensor 103 a, and sends the determined steering angle data to thesteering ECUs 201 c and 202 c. The steering ECUs 201 c and 202 c drivethe motors 201 a and 202 a in the respective right and left steeringunits 201 and 202 to make actual steering angles detected by therespective actual steering angle sensors 201 b and 202 b equal to thereceived steering angles.

On the other hand, in the assisted marine vessel maneuvering mode, thelever position sensors 102 c and 102 d detect the positions of therespective operation levers (right operation lever 102 a and leftoperation lever 102 b) in Step S3. The positional information of theoperation levers is sent from the lever position sensors 102 c and 102 dto the hull ECU 104. Then, in Step S4, the hull ECU 104 sets a targetpivoting speed based on the received positional information of theoperation levers. That is, the hull ECU 104 sets the target pivotingspeed according to the lever position difference ΔL. In Step S5, thehull ECU 104 further sets a target travel speed based on the positionalinformation of the operation levers 102 a and 102 b. That is, when theoperation levers 102 a and 102 b are on the same side with respect tothe neutral position, the hull ECU 104 sets the target travel speedaccording to the position (minimum displacement position Lmin) of one ofthe operation levers having a smaller amount of displacement withrespect to the neutral position. When the operation levers 102 a and 102b are on opposite sides with respect to the neutral position, the hullECU 104 sets the target travel speed to zero, as described above.

Next, the hull ECU 104 performs pivoting moment generation control toapply a moment for achieving the obtained target pivoting speed to thehull 100 (Step S6). The hull ECU 104 further performs translationsuppression control to suppress the translation of the hull 100 so thatthe hull 100 travels at the target travel speed (the hull 100 stops ifthe target travel speed is zero) (Step S7).

In Step S8, the hull ECU 104 also determines whether or not the steeringoperation mechanism 103 is operated based on a detection result from theoperation angle sensor 103 a. If the steering operation mechanism 103 isrotated by a predetermined angle or more, the hull ECU 104 determinesthat the steering operation mechanism 103 is operated by the operator,and the routine proceeds to Step S9 to switch to the control under thenormal marine vessel maneuvering mode. If the steering operationmechanism 103 is not rotated by the predetermined angle or more, thehull ECU 104 determines that the steering operation mechanism 103 is notoperated by the operator, and the routine returns to Step S1. Steps S1to S9 will thereafter be repeated.

FIG. 17 is a flow chart illustrating pivoting moment generation controland translation suppression control (Steps S6 and S7 in FIG. 16) indetail. The pivoting moment generation control includes calculation of atarget pivoting moment (Step S61). The hull ECU 104 calculates a targetpivoting moment required to achieve the target pivoting speed that isobtained based on the lever position difference ΔL. This processing mayinclude reading a target moment corresponding to the target pivotingspeed out of a prepared map. The map may be stored in a memory unit 104Mof the hull ECU 104 in advance (see FIG. 5).

The hull ECU 104 selects one outboard motor (right outboard motor 301 orleft outboard motor 302) to generate a moment thereby based on thecalculated target pivoting moment (Step S62). The selected andnon-selected outboard motors will hereinafter be referred to,respectively, as “selected outboard motor” and “non-selected outboardmotor.” The steering angle of the non-selected outboard motor will becontrolled such that its propulsive force follows a straight line thatpasses through the rotational center of the hull 100. That is, in thisprocessing example, the propulsive force of the non-selected outboardmotor hardly contributes to the generation of the moment.

The hull ECU 104 calculates a steering angle of the selected outboardmotor required to achieve the target pivoting moment when the selectedoutboard motor is driven at a minimum engine speed (Step S63). Theminimum engine speed is an engine speed to be set when the operationlevers 102 a and 102 b are operated to their shift-in positions. Theshift-in position is a position at which the shift state switches fromthe neutral to the forward or reverse drive state when the operationlever 102 a or 102 b is operated forward or backward from the neutralposition. The engine speed at the shift-in position may be called trawlspeed. In general, the minimum engine speed belongs to a speed rangefrom the idle speed to the trawl speed. For the purpose of internalarithmetic processing in the hull ECU 104, the minimum engine speed isexpressed with a positive sign when the shift state is in the forwarddrive state, and is expressed with a negative sign when the shift stateis in the reverse drive state.

The hull ECU 104 compares the absolute value of the calculated steeringangle with the maximum absolute steering angle (e.g., about 25 degrees)of each outboard motor to determine if it is possible to generate thetarget pivoting moment only by steering control (Step S64). If it is notpossible to generate the target pivoting moment even at the maximumabsolute steering angle, the hull ECU 104 further calculates an enginespeed to be added (additional engine speed) (Step S65). The additionalengine speed is positive when the target shift state is in the forwarddrive state, while it is negative when the target shift state is in thereverse drive state. The additional engine speed is an engine speed tobe added to the minimum engine speed to compensate for a shortage in thepropulsive force generated at the minimum engine speed. If it ispossible to generate the target pivoting moment at an absolute steeringangle equal to or smaller than the maximum absolute steering angle, thecalculation of the additional engine speed (in Step S65) is omitted. Thetarget engine speed and target steering angle of the selected outboardmotor are thus set.

The translation suppression control includes calculation of ananteroposterior component of the propulsive force generated by theselected outboard motor (Step S66). The anteroposterior component is acomponent of the propulsive force generated by the selected outboardmotor in the longitudinal direction of the hull 100. The hull ECU 104calculates an anteroposterior component (orthogonal projection of thepropulsive force to the hull centerline 21) based on the propulsiveforce generated by the selected outboard motor and the steering angle ofthe selected outboard motor. The hull ECU 104 further calculates apropulsive force to be generated by the non-selected outboard motor withwhich the resultant force of the anteroposterior components of theselected and non-selected outboard motors corresponds to the targettravel speed (Step S67). If the target travel speed is zero, thepropulsive force to be generated by the non-selected outboard motor isto be calculated to cancel the anteroposterior component of the selectedoutboard motor. Based on this calculated propulsive force, the targetengine speed of the non-selected outboard motor is calculated (StepS68). The target steering angle of the non-selected outboard motor isset such that the direction of the propulsive force of the non-selectedoutboard motor follows a straight line that passes through therotational center of the hull 100.

The hull ECU 104 transmits the target steering angles of the selectedand non-selected outboard motors to the steering ECUs 201 c and 202 cvia the LAN 10. The hull ECU 104 also transmits target shift states andtarget throttle opening degrees corresponding to the target enginespeeds of the selected and non-selected outboard motors to the outboardmotor ECUs 308, 308 via the LAN 10 (Step S69). The target shift state isin the forward drive state when the target engine speed is positive, andis in the reverse drive state when the target engine speed is negative.The steering ECUs 201 c and 202 c set the steering angles of theoutboard motors 301 and 302 to their respective target steering angles.The outboard motor ECUs 308, 308 set the shift states and throttleopening degrees of the outboard motors 301 and 302 to their respectivetarget values.

FIG. 18 is a graph illustrating an example of the relationship betweenthe target pivoting moment and the steering angle of each outboardmotor. The hull ECU 104 performs the processing of Steps S63 and S64 inFIG. 17 according to, for example, the features shown in FIG. 18.

For example, the minimum engine speed preferably is about 750 rpm. Also,the maximum absolute steering angle of each outboard motor in onedirection preferably is about 25 degrees. The greater the steering angleof each outboard motor, the larger the moment can be applied to the hull100. However, if the minimum engine speed is retained, the moment at themaximum absolute steering angle is an upper limit. Hence, for a targetpivoting moment over a threshold value corresponding to the minimumengine speed and the maximum absolute steering angle, an additionalengine speed is set to increase the propulsive force. That is, thetarget steering angle is set to a value corresponding to the maximumabsolute steering angle, and the engine speed and therefore thepropulsive force is increased to achieve the target pivoting moment.

If the target pivoting moment is equal to or smaller than the thresholdvalue, the target pivoting moment can be achieved by increasing theengine speed instead of turning the outboard motor to its maximumabsolute steering angle. This feature is shown by a phantom line in FIG.18. In this case, however, the anteroposterior component of the selectedoutboard motor increases with the increase in the engine speed. It istherefore necessary to increase the engine speed of the non-selectedoutboard motor to cancel the anteroposterior component. Consequently,from the viewpoint of energy savings, it is preferable to achieve thetarget pivoting moment, if possible at the minimum engine speed, bychanging the steering angle at the minimum engine speed.

In the assisted marine vessel maneuvering mode, not only the shiftstates and propulsive forces but also the steering angles of the rightand left outboard motors 301 and 302 are thus controlled based ondetection results from the two lever position sensors 102 c and 102 d.More specifically, the target pivoting speed and target travel speed areset according to the operational positions of the right and leftoperation levers 102 a and 102 b, and accordingly the shift states,propulsive forces (engine speeds), and steering angles of the right andleft outboard motors 301 and 302 are controlled. This allows thepropulsive forces of the outboard motors 300 to act effectively on thehull 100. This also allows the hull 100 to have a smaller turning radiusand the behavior of the hull 100 to be changed quickly, whereby themovement of the marine vessel can be controlled finely. In addition,since the marine vessel can be controlled only by operating theoperation levers (right operation lever 102 a and left operation lever102 b), there is no need to operate the steering operation mechanism103. It is therefore possible to improve the operability when finelycontrolling the movement of the marine vessel. Since the marine vesselcan be controlled only by operating the operation levers, there is alsono need to provide another operation system, such as a cross-shaped key,separately from the operation levers. This can prevent the marine vesselpropulsion system from having a complex structure, and no complicatedoperations are required.

Also, in the assisted marine vessel maneuvering mode, the hull 100pivots counterclockwise when the right operation lever 102 a ispositioned anterior to the left operation lever 102 b, while pivotingclockwise when the left operation lever 102 b is positioned anterior tothe right operation lever 102 a. That is, the shift states, enginespeeds, and steering angles of the outboard motors 301 and 302 arecontrolled to realize these pivoting behaviors. In addition, the targetpivoting speed is set according to the lever position difference ΔLbetween the operation levers. Therefore, the relationship with regard tothe positional relationship between the operation levers 102 a and 102 band the pivoting behavior of the hull 100 is similar to that in thenormal marine vessel maneuvering mode. This allows the operator toeasily imagine the behavior of the marine vessel according to theoperation of the operation levers.

Further, in the assisted marine vessel maneuvering mode, when the rightand left operation levers 102 a and 102 b are on the same side withrespect to the neutral position, the outboard motors 301 and 302 arecontrolled such that the hull 100 drives in the direction in which thelevers are operated. In this case, the target travel speed is furtherset according to the position of one of the operation levers having asmaller amount of displacement with respect to the neutral position.Therefore, the relationship between the operational positions of theoperation levers 102 a and 102 b and the travel speed of the hull 100 isalso similar to that in the normal marine vessel maneuvering mode. Thisallows the operator to easily imagine the behavior of the marine vesselaccording to the operation of the operation levers.

Thus, in the assisted marine vessel maneuvering mode, the operator canset the target pivoting speed and target travel speed through anintuitive operation.

When the right and left operation levers 102 a and 102 b are on oppositesides with respect to the neutral position, the target travel speed isset to zero, so that the hull 100 pivots with no substantialdisplacement. This allows the pivoting behavior corresponding to theoperator's own intentions to be realized by operating only the operationlevers in the same manner as in the normal marine vessel maneuveringmode.

FIG. 19 is a schematic plan view of a marine vessel in which threeoutboard motors are mounted on a hull 100. In this marine vessel, aright outboard motor 301, a left outboard motor 302, and a centeroutboard motor 400 are mounted at the stern of the hull 100. Forexample, in the assisted marine vessel maneuvering mode, the steeringangle and shift state of the center outboard motor 400 are controlled,respectively, to be zero degrees and the neutral state. The right andleft outboard motors 301 and 302 are controlled in the same manner as inthe above-described marine vessel having two outboard motors. In thisassisted marine vessel maneuvering mode, the behavior of the marinevessel is the same as that of the above-described marine vessel havingtwo outboard motors. It is noted that FIG. 19 shows an operation examplewhen the right operation lever 102 a is positioned anterior to theneutral position and the left operation lever 102 b is in the neutralposition (see FIG. 12).

FIG. 20 is a schematic plan view of a marine vessel in which fouroutboard motors 300 are mounted on a hull 100. In this marine vessel, aright outboard motor 301, a left outboard motor 302, a right-centeroutboard motor 401, and a left-center outboard motor 402 are mounted atthe stern of the hull 100. The right outboard motor 301 and theright-center outboard motor 401 are arranged on the right of thecenterline 21 of the hull 100 to form a right outboard motor group. Theright outboard motor 301 is arranged in the rightmost position. Theright-center outboard motor 401 is arranged nearer the centerline 21than the right outboard motor 301. The left outboard motor 302 and theleft-center outboard motor 402 are arranged on the left of thecenterline 21 of the hull 100 to form a left outboard motor group. Theleft outboard motor 302 is arranged in the leftmost position. Theleft-center outboard motor 402 is arranged nearer the centerline 21 thanthe left outboard motor 302.

In the assisted marine vessel maneuvering mode, the right andright-center outboard motors 301 and 401, which form the right outboardmotor group, are controlled in the same manner as the right outboardmotor 301 in the above-described marine vessel having two outboardmotors. Similarly, in the assisted marine vessel maneuvering mode, theleft and left-center outboard motors 302 and 402, which form the leftoutboard motor group, are controlled in the same manner as the leftoutboard motor 302 in the above-described marine vessel having twooutboard motors. That is, the right and right-center outboard motors 301and 401 correspond to a “first propulsion device” according to apreferred embodiment of the present invention, and the left andleft-center outboard motors 302 and 402 correspond to a “secondpropulsion device” according to a preferred embodiment of the presentinvention.

Next will be described an operation example when, for example, the rightoperation lever 102 a is positioned anterior to the neutral position andthe left operation lever 102 b is in the neutral position (see FIG. 12).The shift states of the right and right-center outboard motors 301 and401, which form the right outboard motor group, are controlled to theforward drive state. The steering angles of the right and right-centeroutboard motors 301 and 401 are also controlled such that the directionsof their propulsive forces follow respective straight lines 301 a and401 a that pass through the rotational center 20 of the hull 100. On theother hand, the shift states of the left and left-center outboard motors302 and 402, which form the left outboard motor group, are controlled tothe reverse drive state. The left and left-center outboard motors 302and 402 are also controlled to have the same steering angle. Thissteering angle is set such that the directions of the propulsive forcesdo not include the rotational center 20 of the hull 100. Morespecifically, the propulsive forces of the left and left-center outboardmotors 302 and 402 act backward along straight lines 302 a and 402 athat pass on the left of the rotational center 20 of the hull 100. Thiscauses the hull 100 to be applied with a counterclockwise moment and topivot so that its stern moves leftward.

The arrangement of the first preferred embodiment can thus be appliedeasily to marine vessels including three or more outboard motors.

Second Preferred Embodiment

In a second preferred embodiment of the present invention, the controlunder the assisted marine vessel maneuvering mode is different from thatin the above-described first preferred embodiment. Hence, the secondpreferred embodiment will be described by referring again to FIGS. 1 to5 and redundant descriptions will be omitted.

The control of the marine vessel propulsion system according to thesecond preferred embodiment under the assisted marine vessel maneuveringmode will be described with reference to FIGS. 21 and 22. It is notedthat the “propulsive direction” indicated by the arrows in FIG. 21 is adirection of a propulsive force applied to the hull 100 by the right andleft outboard motors 301 and 302. The length of each arrow representsthe magnitude of a propulsive force by the right and left outboardmotors 301 and 302.

In the assisted marine vessel maneuvering mode, the steering angles,shift states, and throttle opening degrees of the respective outboardmotors 300 (right outboard motor 301 and left outboard motor 302) arecontrolled such that the hull exhibits a behavior pattern correspondingto the positional relationship between the operation levers. That is,the steering angles, shift states, and throttle opening degrees of therespective outboard motors 300 (right outboard motor 301 and leftoutboard motor 302) with which the hull 100 exhibits a predeterminedbehavior pattern are preset and stored in the hull ECU 104correspondingly to the positional relationship between the operationlevers. Such configuration information is stored in the memory unit 104Mincluded in the hull ECU 104 (see FIG. 5). FIG. 22 shows configurationinformation stored in the memory unit 104M (where throttle openingdegrees are not shown). The positional relationship between theoperation levers includes the position of the right operation lever 102a, the position of the left operation lever 102 b, and the positions ofthe right and left operation levers 102 a and 102 b relative to eachother. The hull ECU 104 acquires the positional relationship between theoperation levers based on detection results from the lever positionsensors 102 c and 102 d and reads configuration information (steeringangles, shift states, and throttle opening degrees) corresponding to thepositional relationship out of the memory unit 104M. This readoutconfiguration information is transmitted to the steering ECUs 201 c and202 c and the outboard motor ECUs 308 via the LAN 10. Then, the motors201 a and 202 a in the respective right and left steering units 201 and202 and the outboard motors 300 (right outboard motor 301 and leftoutboard motor 302) are controlled such that the hull 100 exhibits abehavior pattern corresponding to the positional relationship.

In the assisted marine vessel maneuvering mode, the steering angles,shift states, and throttle opening degrees of the outboard motors 300are controlled based on the positional relationship between the twooperation levers. For this reason, as shown in FIG. 22, the position ofthe right operation lever 102 a (forward drive position, reverse driveposition, or neutral position) does not necessarily correspond to theshift state of the right outboard motor 301 (forward drive (F), reversedrive (R), or neutral (N)), unlike the normal marine vessel maneuveringmode. Also, the position of the right operation lever 102 a does notalso necessarily correspond to the throttle opening degree of the rightoutboard motor 301, unlike the normal marine vessel maneuvering mode.Similarly, the position of the left operation lever 102 b does notnecessarily correspond to the shift state and/or throttle opening degreeof the left outboard motor 302. The control will hereinafter bedescribed in detail.

When the shift state of the right outboard motor 301 corresponding tothe position of the right operation lever 102 a is the same as the shiftstate of the left outboard motor 302 corresponding to the position ofthe left operation lever 102 b, the operation is the same as in thenormal marine vessel maneuvering mode. That is, the steering angle ofthe outboard motors 300 is not changed to be in the neutral position,and only the shift states and throttle opening degrees of the outboardmotors 300 are changed. Specifically, when both the right and leftoperation levers 102 a and 102 b are in the neutral position, the shiftstates of the right and left outboard motors 301 and 302 are bothcontrolled to be neutral (N). In this case, the throttle opening degreesof the right and left outboard motors 301 and 302 are both controlled tobe in the fully-closed state (with an opening degree of 0%). When boththe right and left operation levers 102 a and 102 b are in the forwardor reverse drive position, the shift states of the right and leftoutboard motors 301 and 302 are both controlled to be forward drive (F)or reverse drive (R). Then, the right and left outboard motors 301 and302 are controlled to have their respective throttle opening degrees (0to 100%) that correspond to the amount of displacement of the respectiveoperation levers with respect to the neutral position.

In the assisted marine vessel maneuvering mode, when the position of theright operation lever 102 a (forward drive position, reverse driveposition, or neutral position) is different from the position of theleft operation lever 102 b (forward drive position, reverse driveposition, or neutral position), the control is different from that underthe normal marine vessel maneuvering mode. That is, the steering angles,shift states, and throttle opening degrees of the outboard motors 300are controlled such that the hull 100 exhibits a behavior pattern presetcorrespondingly to the positional relationship between the operationlevers.

For example, as indicated by (A1) in FIGS. 21 and 22, when the right andleft operation levers 102 a and 102 b are, respectively, in the neutraland forward drive positions, the operation runs as follows. The behaviorof the hull 100 preset correspondingly to this positional relationshipbetween the operation levers is a movement (translation) in the(left-forward) direction from the right operation lever 102 a in theneutral position to the left operation lever 102 b on the forward driveside. That is, the steering angles, shift states, and throttle openingdegrees of the outboard motors 300 are controlled such that the hull 100is translated left-forward. Translation means that the hull 100 moveswithout substantially pivoting.

In the case above, the steering angle of the right outboard motor 301 ischanged to be about +10 degrees, for example, while the steering angleof the left outboard motor 302 is changed to be about −10 degrees, forexample. That is, the steering angles of the outboard motors 300 arechanged such that the rear end portions of the right and left outboardmotors 301 and 302 are moved away from each other. In this case, thepropulsive force vectors of the right and left outboard motors 301 and302 are both directed to the rotational center of the hull 100. Thiscauses the hull 100 to be translated with little pivoting. It is notedthat the steering angle takes a positive value when the rear endportions (propellers 307) of the outboard motors 301 and 302 are turnedrightward with respect to the longitudinal direction of the hull 100,while taking a negative value when turned leftward with respect to thelongitudinal direction of the hull 100.

Although the right and left operation levers 102 a and 102 b are,respectively, in the neutral and forward drive positions, the shiftstates of the outboard motors 301 and 302 do not correspond to thepositions. That is, the shift states of the right and left outboardmotors 301 and 302 are controlled, respectively, to be forward drive (F)and reverse drive (R). Also, the throttle opening degrees of the rightand left outboard motors 301 and 302 are also controlled to theirrespective predetermined preset values, regardless of the positions ofthe operation levers. In the behavior pattern (A1), the throttle openingdegree of the right outboard motor 301 is controlled to be greater thanthat of the left outboard motor 302. In this case, the resultant forceof the propulsive forces of the right and left outboard motors 301 and302 causes the hull 100 to be translated left-forward.

As indicated by (A2) in FIG. 22, when the right and left operationlevers 102 a and 102 b are, respectively, in the forward drive andneutral positions, the operation runs as follows. The behavior of thehull 100 preset correspondingly to this positional relationship betweenthe operation levers is a movement (translation) in the (right-forward)direction from the left operation lever 102 b in the neutral position tothe right operation lever 102 a on the forward drive side. That is, thesteering angle of the right outboard motor 301 is changed to be about+10 degrees, for example, while the steering angle of the left outboardmotor 302 is changed to be about −10 degrees, for example. Although theright and left operation levers 102 a and 102 b are, respectively, inthe forward drive and neutral positions, the shift states of the rightand left outboard motors 301 and 302 are controlled, respectively, to bereverse drive (R) and forward drive (F). In the behavior pattern (A2),the throttle opening degree of the right outboard motor 301 iscontrolled to be smaller than that of the left outboard motor 302. Inthis case, the resultant force of the propulsive forces of the right andleft outboard motors 301 and 302 causes the hull 100 to be translatedright-forward.

Also, as indicated by (B1) in FIGS. 21 and 22, when the right and leftoperation levers 102 a and 102 b are, respectively, in the neutral andreverse drive positions, the operation runs as follows. The behavior ofthe hull 100 preset correspondingly to this positional relationshipbetween the operation levers is a movement (translation) in the(left-backward) direction from the right operation lever 102 a in theneutral position to the left operation lever 102 b on the reverse driveside. That is, the steering angles, shift states, and throttle openingdegrees of the outboard motors 300 are controlled such that the hull 100is translated left-backward.

In the case above, the steering angle of the right outboard motor 301 ischanged to be about +10 degrees, for example, while the steering angleof the left outboard motor 302 is changed to be about −10 degrees, forexample. Although the right and left operation levers 102 a and 102 bare, respectively, in the neutral and reverse drive positions, the shiftstates of the right and left outboard motors 301 and 302 are controlled,respectively, to be forward drive (F) and reverse drive (R). In thebehavior pattern (B1), the throttle opening degree of the left outboardmotor 302 is controlled to be greater than that of the right outboardmotor 301. In this case, the resultant force of the propulsive forces ofthe right and left outboard motors 301 and 302 causes the hull 100 to betranslated left-backward.

Further, as indicated by (B2) in FIG. 22, when the right and leftoperation levers 102 a and 102 b are, respectively, in the reverse driveand neutral positions, the operation runs as follows. The behavior ofthe hull 100 preset correspondingly to this positional relationshipbetween the operation levers is a movement (translation) in the(right-backward) direction from the left operation lever 102 b in theneutral position to the right operation lever 102 a on the reverse driveside. That is, the steering angle of the right outboard motor 301 ischanged to be about +10 degrees, for example, while the steering angleof the left outboard motor 302 is changed to be about −10 degrees, forexample. Although the right and left operation levers 102 a and 102 bare, respectively, in the reverse drive and neutral positions, the shiftstates of the right and left outboard motors 301 and 302 are controlled,respectively, to be reverse drive (R) and forward drive (F). In thebehavior pattern (B2), the throttle opening degree of the right outboardmotor 301 is controlled to be greater than that of the left outboardmotor 302. In this case, the resultant force of the propulsive forces ofthe right and left outboard motors 301 and 302 causes the hull 100 to betranslated right-backward.

As indicated by (C1) in FIGS. 21 and 22, when the right and leftoperation levers 102 a and 102 b are, respectively, in the reverse andforward drive positions, the shift states of the right and left outboardmotors 301 and 302 are controlled, respectively, to be reverse drive (R)and forward drive (F). In this case, the steering angle of the rightoutboard motor 301 is changed to be about −10 degrees, for example,while the steering angle of the left outboard motor 302 is changed to beabout +10 degrees, for example, as indicated by (C1) in FIG. 22. Thatis, when the right and left operation levers 102 a and 102 b are,respectively, in the reverse and forward drive positions, the steeringangles of the right and left outboard motors 301 and 302 are changedsuch that the rear end portions of the right and left outboard motors301 and 302 are brought close to each other. Also, the shift states ofthe right and left outboard motors 301 and 302 are controlled,respectively, to be reverse drive (R) and forward drive (F)correspondingly to the position (reverse drive position) of the rightoperation lever 102 a and the position (forward drive position) of theleft operation lever 102 b. Also, the throttle opening degrees of theright and left outboard motors 301 and 302 are also controlled to theirrespective predetermined preset values, regardless of the positions ofthe operation levers. In the behavior pattern (C1), the throttle openingdegrees of the right and left outboard motors 301 and 302 are the same.However, since the thrust (propulsive force) when the shift state is inreverse drive (R) is smaller than that when the shift state is inforward drive (F), the throttle opening degree of the right outboardmotor 301 may be set greater than that of the left outboard motor 302.

In the behavior pattern (C1), the steering angles, shift states, andthrottle opening degrees of the outboard motors 300 are thus controlledsuch that the hull 100 is applied with a forward drive propulsive forceon the left side and a reverse drive propulsive force on the right side,whereby the behavior of the hull 100 is a rightward pivoting motionabout the stern of the hull 100. Since the steering angles of the rightand left outboard motors 301 and 302 are controlled to follow thedirection of the pivoting motion of the hull 100, the propulsive forcesof the right and left outboard motors 301 and 302 are appliedeffectively in the pivoting direction of the hull 100.

Similarly, as indicated by (C2) in FIG. 22, when the right and leftoperation levers 102 a and 102 b are, respectively, in the forward andreverse drive positions, the steering angle of the right outboard motor301 is changed to be about −10 degrees, for example, while the steeringangle of the left outboard motor 302 is changed to be about +10 degrees,for example. The shift states of the right and left outboard motors 301and 302 are controlled, respectively, to be forward drive (F) andreverse drive (R) correspondingly to the position (forward driveposition) of the right operation lever 102 a and the position (reversedrive position) of the left operation lever 102 b. The throttle openingdegrees of the right and left outboard motors 301 and 302 are alsocontrolled to their respective predetermined preset values, regardlessof the positions of the operation levers. In the behavior pattern (C2),the throttle opening degrees of the right and left outboard motors 301and 302 are the same. However, since the thrust (propulsive force) whenthe shift state is in reverse drive (R) is smaller than that when theshift state is in forward drive (F), the throttle opening degree of theleft outboard motor 302 may be set greater than that of the rightoutboard motor 301.

In the behavior pattern (C2), the hull 100 is applied with a reversedrive propulsive force on the left side and a forward drive propulsiveforce on the right side, whereby the behavior of the hull 100 is aleftward pivoting motion about the stern of the hull 100. Since thesteering angles of the right and left outboard motors 301 and 302 arecontrolled to follow the direction of the pivoting motion of the hull100, the propulsive forces of the right and left outboard motors 301 and302 are applied effectively in the pivoting direction of the hull 100.

As described heretofore, when the right and left operation levers 102 aand 102 b are, respectively, in one and the other of the forward andreverse drive positions, the steering angles of the right and leftoutboard motors 301 and 302 are changed such that the rear end portionsof the right and left outboard motors 301 and 302 are brought close toeach other. The vector directions of the propulsive forces generated bythe right and left outboard motors 300 do not include the rotationalcenter of the hull 100 (that approximately coincides with the center ofgravity of the hull 100, for example). Therefore, the propulsive forcesgenerated by the right and left outboard motors 300 apply a moment abouta vertical axis to the hull 100. This causes the hull 100 to pivot withlittle displacement.

It is noted that the behavior patterns (C1) and (C2) are examples ofcontrol when the two operation levers are, respectively, in the forwardand reverse drive positions. The steering angles, shift states, andthrottle opening degrees of the outboard motors 300 may be controlledsuch that the hull 100 exhibits a behavior other than the pivotingmotions.

In the second preferred embodiment, the amount of change in the steeringangle of each outboard motor 300 is preferably fixed at about 10degrees, for example, regardless of the amount of displacement of thecorresponding operation lever with respect to the neutral position(i.e., throttle opening degree). In the marine vessel propulsion systemadopting two outboard motors 300, when the steering angles of the rightand left outboard motors 301 and 302 are changed by, for example, about13 degrees or more so that the rear end portions thereof are broughtclose to each other, the right and left outboard motors 301 and 302interfere with each other. Accordingly, the amount of change in thesteering angle of each outboard motor 300 is preferably set to about 12degrees or less, for example.

Next will be described the operational control for the marine vesselpropulsion system according to the second preferred embodiment withreference to FIGS. 22 and 23.

In Step S11, the hull ECU 104 determines whether or not the selectorswitch 105 is ON. If the selector switch 105 is OFF, the routine goes toStep S17 and the control under the normal marine vessel maneuvering modeis performed. On the other hand, if the selector switch 105 is ON, thecontrol under the assisted marine vessel maneuvering mode is performedin Step S12.

In the normal marine vessel maneuvering mode, the hull ECU 104determines the shift states and throttle opening degrees of the rightand left outboard motors 301 and 302 based on positional information ofthe operation levers detected by the lever position sensors 102 c and102 d. These determined shift states and throttle opening degrees aresent to the outboard motor ECUs 308. The outboard motor ECUs 308 controlthe motors 303 a and 305 a based on the received shift states andthrottle opening degrees to drive the throttle valve 303 b and theforward-reverse switching mechanism 305. The hull ECU 104 alsodetermines the steering angles of the right and left outboard motors 301and 302 based on an operation angle detected by the operation anglesensor 103 a, and sends the determined steering angle data to thesteering ECUs 201 c and 202 c. The steering ECUs 201 c and 202 c drivethe motors 201 a and 202 a in the respective right and left steeringunits 201 and 202 to make actual steering angles detected by therespective actual steering angle sensors 201 b and 202 b equal to thereceived steering angles.

On the other hand, in the assisted marine vessel maneuvering mode, thelever position sensors 102 c and 102 d detect the positions of therespective operation levers (right operation lever 102 a and leftoperation lever 102 b) in Step S13. The positional information of theoperation levers is sent from the lever position sensors 102 c and 102 dto the hull ECU 104. Then, in Step S14, the hull ECU 104 determines theshift states, throttle opening degrees, and steering angles of the rightand left outboard motors 301 and 302 based on the received positionalinformation of the operation levers and the relationship shown in FIG.22.

Next, in Step S15, the hull ECU 104 sends the determined shift statesand throttle opening degrees to the outboard motor ECUs 308 in the rightand left outboard motors 301 and 302. The outboard motor ECUs 308 drivethe motor 305 a for the forward-reverse switching mechanism 305 and themotor 303 a for the throttle valve 303 b to achieve the received shiftstates and throttle opening degrees. The hull ECU 104 also sends thedetermined steering angles to the steering ECUs 201 c and 202 c in therespective right and left steering units 201 and 202. The steering ECUs201 c and 202 c drive the motors 201 a and 202 a in the respective rightand left steering units 201 and 202 to make actual steering anglesdetected by the respective actual steering angle sensors 201 b and 202 bequal to the received steering angles.

In Step S16, the hull ECU 104 determines whether or not the steeringoperation mechanism 103 is operated based on a detection result from theoperation angle sensor 103 a. If the steering operation mechanism 103 isrotated by a predetermined angle or more, the hull ECU 104 determinesthat the steering operation mechanism 103 is operated by the operator,and the routine proceeds to Step S17 to switch to the control under thenormal marine vessel maneuvering mode. If the steering operationmechanism 103 is not rotated by the predetermined angle or more, thehull ECU 104 determines that the steering operation mechanism 103 is notoperated by the operator, and the routine returns to Step S11. Steps S11to S17 will thereafter be repeated.

In the assisted marine vessel maneuvering mode, the steering angles,shift states, and propulsive forces of the respective multiple outboardmotors 300 are controlled such that the hull 100 exhibits a behaviorpattern preset correspondingly to the positional relationship betweenthe two operation levers (right operation lever 102 a and left operationlever 102 b), as described above. Therefore, the operator, if he/shewants the hull 100 to exhibit a predetermined behavior such as pivotingor lateral movement, is only required to operate the operation levers soas to be a positional relationship corresponding to the desiredbehavior. In response to this lever operation, the steering angles,shift states, and propulsive forces of the outboard motors 300 arecontrolled automatically to be appropriate to cause the hull 100 toexhibit the desired behavior. This arrangement allows the propulsiveforces of the outboard motors 300 to be used effectively when the hull100 pivots or moves laterally, for example. This allows the behavior(e.g., pivoting motion) of the hull 100 to be changed quickly and highlyresponsively. As a result, the movement of the marine vessel can befinely controlled.

In addition, since the marine vessel can be controlled only by operatingthe operation levers, there is no need to operate the steering operationmechanism 103. It is therefore possible to improve the operability whenfinely controlling the movement of the marine vessel. There is also noneed to provide another operation system, such as a cross-shaped key,separately from the operation levers, which can prevent the marinevessel propulsion system from having a complex structure. Since there isno need to add another operation system, no complicated operations arerequired. Therefore, the second preferred embodiment can improve theoperability when finely controlling the movement of the marine vesselwhile preventing the marine vessel propulsion system from having acomplex structure.

Also, in the second preferred embodiment, the positions of the operationlevers 102 a and 102 b do not necessarily correspond to the shift statesof the respective outboard motors 300 in the assisted marine vesselmaneuvering mode, as described above. That is, the steering angles,shift states, and propulsive forces of the respective multiple outboardmotors 300 are controlled such that the hull 100 exhibits a behaviorpattern corresponding to the positional relationship between theoperation levers 102 a and 102 b. In the assisted marine vesselmaneuvering mode, the operator may operate the operation levers so as tobe a positional relationship corresponding to a behavior into whichhe/she wants to bring the hull 100 without regard to the shift states ofthe outboard motors 300. This allows the hull 100 to exhibit the desiredbehavior easily.

Further, in the second preferred embodiment, when the shift statecorresponding to the position of the right operation lever 102 a is thesame as the shift state corresponding to the position of the leftoperation lever 102 b in the assisted marine vessel maneuvering mode,the hull 100 moves straight (forward or backward). When the shift statesare different from each other, the hull 100 exhibits a behavior pattern(other than straight drive) corresponding to the positional relationshipbetween the right and left operation levers 102 a and 102 b. Since thisbehavior is similar to a behavior of the hull 100 through a normaloperation of the operation levers, it is possible to provide theoperator with an improved, more natural feeling.

Also, in the second preferred embodiment, when the right and leftoperation levers 102 a and 102 b are, respectively, in the neutralposition and a position other than the neutral position (on the forwardor reverse drive side) in the assisted marine vessel maneuvering mode, acharacteristic operation is performed. That is, the steering angles,shift states, and propulsive forces of the respective outboard motors300 are controlled such that the hull 100 moves in a directioncorresponding to the direction from the position of the right operationlever 102 a in the neutral position to the position of the leftoperation lever 102 b in the position other than the neutral position.The operator operates the operation levers such that the direction ofthe straight line from the position of the right operation lever 102 ain the neutral position to the position of the left operation lever 102b corresponds to the (left-forward or left-backward) direction in whichhe/she wants to move the hull 100. This allows the hull 100 to move inthat direction.

The same operation is also performed when the right and left operationlevers 102 a and 102 b are, respectively, in a position other than theneutral position (on the forward or reverse drive side) and the neutralposition in the assisted marine vessel maneuvering mode. That is, thesteering angles, shift states, and propulsive forces of the respectiveoutboard motors 300 are controlled such that the hull 100 moves in adirection corresponding to the direction from the position of the leftoperation lever 102 b in the neutral position to the position of theright operation lever 102 a in the position other than the neutralposition. The operator operates the operation levers such that thedirection of the straight line from the position of the left operationlever 102 b in the neutral position to the position of the rightoperation lever 102 a corresponds to the direction in which he/she wantsto move the hull 100. This allows the hull 100 to move in that(right-forward or right-backward) direction.

Even operators with a poor marine vessel maneuvering skill can thuscontrol the marine vessel easily.

Furthermore, in the second preferred embodiment, when the right and leftoperation levers 102 a and 102 b are, respectively, in the forward andreverse drive positions in the assisted marine vessel maneuvering mode,the shift states of the right and left outboard motors 301 and 302 arecontrolled, respectively, to be the forward and reverse drive states.The steering angles of the right and left outboard motors 301 and 302are further changed such that the rear end portions of the right andleft outboard motors 301 and 302 are brought close to each other.Similarly, when the right and left operation levers 102 a and 102 b are,respectively, in the reverse and forward drive positions, the shiftstates of the right and left outboard motors 301 and 302 are controlled,respectively, to be the reverse and forward drive states. The steeringangles of the right and left outboard motors 301 and 302 are furtherchanged such that the rear end portions of the right and left outboardmotors 301 and 302 are brought close to each other. This arrangementallows the propulsive forces of the right and left outboard motors 301and 302 to act in a pivoting direction of the hull 100. The propulsiveforces of the right and left outboard motors 301 and 302 consequentlyallow the hull 100 to rotate (pivot) quickly and highly responsivelywithout being largely displaced (substantially with no displacement).

Moreover, in the second preferred embodiment, the selector switch 105 isarranged to switch control modes between the normal marine vesselmaneuvering mode and the assisted marine vessel maneuvering mode, asdescribed above. With this arrangement, the operator can run the normalmarine vessel maneuvering mode and use the steering operation mechanism103 for normal marine vessel maneuvering. On the other hand, theoperator, when required to finely control the movement of the marinevessel (such as launching from and docking on shore), can run theassisted marine vessel maneuvering mode and use only the operationlevers for maneuvering. This can improve the convenience for theoperator.

The above-described advantageous effects of the marine vessel propulsionsystem according to the second preferred embodiment will hereinafter bedescribed in more detail with reference to FIG. 24. In FIG. 24, thebehavior of the hull 100 in the normal marine vessel maneuvering mode,in which the steering angles are not controlled according to thepositions of the operation levers, is shown in a manner comparable withthe behavior of the hull 100 in the assisted marine vessel maneuveringmode.

FIG. 24 shows the behavior of the hull 100 when brought alongside a pierunder the assisted and normal marine vessel maneuvering modes. As shownin FIG. 24, in the normal marine vessel maneuvering mode, the hull 100cannot be turned in a small radius, which requires a larger space R tobring the marine vessel alongside the pier. On the other hand, in theassisted marine vessel maneuvering mode, the hull 100 can be turned in asmall radius, which requires only a smaller space S to bring the marinevessel alongside the pier.

Other Preferred Embodiments

The above-disclosed preferred embodiments of the present invention areto be considered in all aspects only as illustrative and notrestrictive. The scope of the present invention is not defined by theabove-described preferred embodiments, but rather by the claims appendedhereto. Further, the present invention includes all the modificationswithin the meaning and scope equivalent to those defined by the appendedclaims.

For example, although the preferred embodiments above describe mainlythe case where two operation levers are preferably used to steer twooutboard motors, the present invention is not restricted thereto. Two ormore operation levers may be used to steer four or more outboard motors,including the cases, for example, where two operation levers are used tosteer four outboard motors (see FIG. 20) and where three operationlevers are used to steer three outboard motors (see FIG. 19).

Although, the preferred embodiments above describe the case whereoutboard motors that generate a propulsive force by rotating a propellerwith a driving force from an engine are preferably adopted, the presentinvention is not restricted thereto. That is, outboard motors and otherpropulsion devices may be adopted that generate a propulsive force byrotating a propeller with a driving force from an electric motor. Notonly propulsion devices that generate a propulsive force by rotating apropeller but also propulsion devices (jet propulsion devices) thatgenerate a propulsive force through jet drive in which water is jettedthrough an injection nozzle may be adopted.

Although, the preferred embodiments above describe the case where amarine vessel maneuvering operator preferably operates the selectorswitch to switch between the normal marine vessel maneuvering mode andthe assisted marine vessel maneuvering mode, the present invention isnot restricted thereto. That is, it may be arranged that the normalmarine vessel maneuvering mode switches automatically to the assistedmarine vessel maneuvering mode if predetermined conditions are met.

Although the second preferred embodiment above describes the case wherethe patterns (A1) and (A2) preferably correspond to lateral-forwardmovement, (B1) and (B2) to lateral-backward movement, and (C1) and (C2)to pivoting moment, the present invention is not restricted thereto.That is, the patterns (A1), (A2), (B1), (B2), (C1), and (C2) may be setcorrespondingly to other hull behaviors. The patterns (A1), (A2), (B1),(B2), (C1), and (C2) may correspond to, for example, lateral movement orturning motion.

Although the preferred embodiments above describe the case where thenormal marine vessel maneuvering mode is preferably switchable to oneassisted marine vessel maneuvering mode, the present invention is notrestricted thereto. For example, multiple assisted marine vesselmaneuvering modes having their respective different relationships withregard to the positional relationship between the operation levers andthe behavior of the hull may be provided and the operator may selectfrom among these multiple assisted marine vessel maneuvering modes.

Although the second preferred embodiment above describes the case wherethe amount of change in the steering angle of each outboard motor ispreferably fixed to about 10 degrees, for example, the present inventionis not restricted thereto. The steering angle may be changed to a valueother than approximately 10 degrees.

Although the second preferred embodiment above describes the case wherethe amount of change in the steering angle of the right outboard motor301 and the amount of change in the steering angle of the left outboardmotor 302 are preferably both set to the same angle (e.g., about 10degrees), the present invention is not restricted thereto. That is, theamount of change in the steering angle of the right outboard motor 301may be different from the amount of change in the steering angle of theleft outboard motor 302.

Although the second preferred embodiment above describes the case wherewhen the shift state corresponding to the position of the rightoperation lever 102 a is different from the shift state corresponding tothe position of the left operation lever 102 b, the steering angles,shift states, and throttle opening degrees of the outboard motors arepreferably controlled such that the hull exhibits a behaviorcorresponding to the positional relationship between the operationlevers, the present invention is not restricted thereto. For example,even when the shift states corresponding to the positions of therespective right and left operation levers 102 a and 102 b may be thesame (e.g., both in the forward drive position), the positions of theright and left operation levers 102 a and 102 b may be different (i.e.,the throttle opening degrees of the right and left outboard motors 301and 302 may be different). In this case, the steering angles, shiftstates, and throttle opening degrees of the outboard motors may bechanged such that the hull exhibits a behavior corresponding to thepositional relationship between the right and left operation levers.

Also in the case above, the steering angles, shift states, andpropulsive forces of the respective multiple outboard motors 300 may becontrolled such that the hull 100 moves in a direction corresponding tothe direction from the position of the right operation lever 102 a tothe position of the left operation lever 102 b (or the direction fromthe position of the left operation lever 102 b to the position of theright operation lever 102 a). In this case, the operator operates theright and left operation levers 102 a and 102 b so as to be aligned in adirection in which he/she wants to move the hull 100. This allows thehull 100 to move in that direction. Even operators with a poor marinevessel maneuvering skill can thus control the marine vessel easily.

Although the second preferred embodiment above describes the case wherethe throttle opening degree is preferably controlled such that therelationship between the amount of displacement of each operation leverand the throttle opening degree in the assisted marine vesselmaneuvering mode is the same as in the normal marine vessel maneuveringmode, the present invention is not restricted thereto. That is, in theassisted marine vessel maneuvering mode, the throttle opening degree maybe controlled to be smaller than in the normal marine vessel maneuveringmode. As shown in FIG. 25, the throttle opening degree may be controlledsuch that the throttle opening degree at the maximum amount ofdisplacement of each operation lever is approximately 30% of the maximumthrottle opening degree in the normal marine vessel maneuvering mode,for example. Similarly, the throttle opening degree in the firstpreferred embodiment above may be controlled such that the throttleopening degree at the minimum displacement position Lmin in the assistedmarine vessel maneuvering mode is smaller than that in the normal marinevessel maneuvering mode. Alternatively, in both the first and secondpreferred embodiments above, an upper limit may preliminarily be set onthe engine speed, and in the assisted marine vessel maneuvering mode,the throttle opening degree may be controlled such that the engine speeddoes not exceed the upper limit.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing the scope andspirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

The present application corresponds to Japanese Patent Application No.2009-014988 filed in the Japan Patent Office on Jan. 27, 2009, and theentire disclosure of the application is incorporated herein byreference.

What is claimed is:
 1. A marine vessel propulsion system comprising: aplurality of propulsion devices arranged to be mounted on a hull so asto enable a steering angle to change; a plurality of operation leversarranged to be operated by a marine vessel maneuvering operator tocontrol the plurality of propulsion devices to have respective shiftstates selected from among a forward drive state, a neutral state, and areverse drive state; a plurality of lever position sensors provided tocorrespond to the plurality of respective operation levers and arrangedto detect positions of the plurality of operation levers; a storage unitarranged to store therein behavior patterns of the hull preset tocorrespond to positional relationships between the plurality ofoperation levers; and a control unit programmed to select among thebehavior patterns based on detection results from the plurality of leverposition sensors, and to control the steering angles and shift states ofthe plurality of respective propulsion devices to correspond to theselected behavior pattern.
 2. The marine vessel propulsion systemaccording to claim 1, wherein the plurality of propulsion devicesinclude a first propulsion device and a second propulsion device whichis different from the first propulsion device; the plurality ofoperation levers include a first operation lever corresponding to thefirst propulsion device and a second operation lever corresponding tothe second propulsion device; and the control unit is programmed toselect among behavior patterns preset to correspond to the positionalrelationships between the first and second operation levers when aposition of the first operation lever is different from a position ofthe second operation lever, and to control the steering angles and shiftstates of the respective first and second propulsion devices tocorrespond to the selected behavior pattern.
 3. The marine vesselpropulsion system according to claim 2, wherein the first and secondoperation levers are arranged laterally; and the control unit isprogrammed to control the steering angles, shift states, and propulsiveforces of the respective first and second propulsion devices, when theposition of the first operation lever is different from the position ofthe second operation lever, such that the hull moves in a directioncorresponding to a direction from the position of the first operationlever to the position of the second operation lever.
 4. The marinevessel propulsion system according to claim 3, wherein the control unitis programmed to control the steering angles, shift states, andpropulsive forces of the respective first and second propulsion devices,when the first operation lever is in the neutral position and the secondoperation lever is in a position other than the neutral position, suchthat the hull moves in a direction corresponding to a direction from theposition of the first operation lever in the neutral position to theposition of the second operation lever in the position other than theneutral position.
 5. The marine vessel propulsion system according toclaim 1, further comprising: a steering operation mechanism arranged tobe operated by the marine vessel maneuvering operator to change thesteering angles of the plurality of respective propulsion devices; anoperation angle sensor arranged to detect an operation angle of thesteering operation mechanism; and a switching unit arranged to switchbetween normal marine vessel maneuvering control and assisted marinevessel maneuvering control; wherein in the normal marine vesselmaneuvering control, the control unit is programmed to control the shiftstates and propulsive forces of the propulsion devices based ondetection results from the plurality of lever position sensors, and tochange the steering angles of the plurality of propulsion devices basedon a detection result from the operation angle sensor; and in theassisted marine vessel maneuvering control, the control unit isprogrammed to select among behavior patterns corresponding to thepositional relationships between the plurality of operation levers basedon detection results from the plurality of lever position sensors, andto control the steering angles and shift states of the plurality ofrespective propulsion devices to correspond to the selected behaviorpattern.
 6. The marine vessel propulsion system according to claim 5,wherein in the assisted marine vessel maneuvering control, the controlunit is programmed to control each of the propulsion devices to have apropulsive force smaller than that corresponding to the position of eachoperation lever in the normal marine vessel maneuvering control.
 7. Themarine vessel propulsion system according to claim 5, wherein in theassisted marine vessel maneuvering control, the control unit isprogrammed to select among behavior patterns preset to correspond to thepositional relationships between the plurality of operation levers,based on detection results from the plurality of lever position sensorsand independently of the relationship between the positions of theoperation levers and the shift states of the propulsion devices in thenormal marine vessel maneuvering control, and to control the steeringangles and shift states of the plurality of respective propulsiondevices to correspond to the selected behavior pattern.
 8. The marinevessel propulsion system according to claim 1, wherein each of thepropulsion devices includes an outboard motor arranged to be mounted onthe hull so as to enable the steering angle to change; each of theoutboard motors includes an engine with a driving force thereof beingadjustable through control of a throttle opening degree, a propellerarranged to be rotated by a driving force from the engine, and aswitching mechanism portion arranged to switch shift states; theoperation levers are arranged to be operated by the marine vesselmaneuvering operator to control the plurality of outboard motors to betheir respective shift states and throttle opening degrees; and thecontrol unit is programmed to select among the behavior patterns basedon detection results from the plurality of lever position sensors, andto control the steering angles and shift states of the plurality ofrespective outboard motors to correspond to the selected behaviorpattern.
 9. A marine vessel comprising: a hull; and the marine vesselpropulsion system according to claim 1 provided on the hull.